Symposium Organizers
Zhongyang Cheng Auburn University
Qiming Zhang The Pennsylvania State University
Siegfried Bauer Johannes-Kepler University Linz
Debra A. Wrobleski Los Alamos National Laboratory
BB1: New Materials and Characterization
Session Chairs
Tuesday PM, December 02, 2008
Grand Ballroom (Sheraton)
9:00 AM - **BB1.1
High Performance Dielectric Elastomers.
Qibing Pei 1
1 Materials Science and Engineering, UCLA, Los Angeles, California, United States
Show AbstractSeveral categories of elastomers have been exploited as dielectric elastomers. Acrylic copolymer, silicone, and thermoplastic block copolymers are notable examples exhibiting distinctive electromechanical transduction. We have focused on improving the 3M VHB acrylic films that have already shown the best overall actuation performance when the films are highly prestrained. Interpenetrating polymer networks (IPN) in which the acrylic network is under high tension balanced by compression of an additive network were investigated for further enhanced actuation performance. The IPN films at zero or norminal external prestrain showed up to 300% actuation strain. The calculated values of maximum actuation energy density and electromechanical coupling factor are 3.5 J/g and 93.7%, respectively. Uniaxial stress relaxation analysis showed significant decrease in viscoelastic loss in comparison with the VHB films, the primary component network in the IPN films. Important actuators enabled by the IPN films will also be reported.
9:30 AM - **BB1.2
Nanoscale Interactions in Ferroelectric Polymers.
Stephen Ducharme 1
1 Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska, United States
Show AbstractThe properties of ferroelectric thin films and nanostructures are receiving increasing attention due in part to advances in nanoscale fabrication and characterization and in part due to the enormous commercial potential for application of highly integrated ferroelectric devices in a wide range of technologies, such as, nonvolatile memories, micro- and nano-electromechanical systems, ultrasonic transducer arrays, and infrared imaging. The purpose of this presentation is to review some of the more remarkable, and potentially useful, discoveries that have come out of studies of nanoscale interactions in ferroelectric copolymers of vinylidene fluoride with trifluoroethylene. These polymers can be structured into films as thin as a nanometer and nanocrystals as small as 8 nm thick by 90 nm in diameter, while maintaining their essential ferroelectric properties -- bistable polarization, piezoelectric response, and pyroelectric response. Piezoresponse force microscopy, for example, has been used to measure nanoscale polarization with a resolution of 5 nm and to pattern arbitrary polarization patterns with a resolution of 50 nm. This work was supported by the Nebraska Research Initiative, the National Science Foundation, and the Department of Energy.
10:00 AM - BB1.3
Real-Time Study of Surface Layer Formation with Nanomechanical Cantilever Sensors.
Joachim Koeser 1 2 , Martin Bammerlin 1 , Felice Mauro Battiston 1 , Urs Hubler 1
1 , Concentris GmbH, Basel Switzerland, 2 School of Life Sciences, University of Applied Sciences Northwestern Switzerland, Muttenz Switzerland
Show AbstractNanomechanical cantilevers are small, microfabricated silicon beams, which transform processes occurring at their surface into a mechanical response with extremely high sensitivity. When studying the formation of surface layers, such as the self-assembly of monolayers or more complex processes like the build-up of layer-by-layer structures or other smart materials, valuable real-time information on the dynamics of these processes can be obtained by employing this unique signal transduction principle. Surface stress occurring within the surface layer can be studied by monitoring the bending of the nanomechanical cantilever (static mode). Simultaneously, measuring changes in the oscillation properties of the cantilever (e.g. resonance frequency, quality factor) provides complementary information about changes in mass load on the cantilever and/or stiffness changes within the layer itself (dynamic mode). Information extracted from both data sets helps to get a better understanding of the layer formation process and provides useful information for the optimization of manufacturing parameters. Additionally, the potential of nanomechanical cantilever sensors as a valuable tool for characterization of surface associated phenomena as well as chemical/biological actuators has been impressively illustrated by examples such as the repeated swelling/collapsing cycles of polymer brushes grown on cantilever sensors or the analysis of forces generated by molecular motors. Recently, commercial tools have become available allowing widespread use of nanomechanical cantilever sensors in these research fields. Here, we will demonstrate the label-free monitoring of dynamic changes during layer formation processes and the characterization of surface structures with nanomechanical cantilevers. The insight into the build-up process of new surface coatings based on nanomaterials provided by cantilever sensors will be demonstrated in particular for the formation of self-assembled monolayers (SAMs) as well as polyelectrolyte multilayers (Layer by Layer formation, LbL).
10:15 AM - BB1.4
Hierarchically Structured, High-Toughness Multilayered Composites from Exponential Layer-by-Layer Assembly.
Paul Podsiadlo 1 , Eugene Kheng 2 , Jungwoo Lee 3 , Kevin Critchley 1 , Ming Qin 1 , Ying Qi 4 , Amit Kaushik 2 , Eric Chuang 1 , Hyoung-Sug Kim 5 , Si-Tae Noh 5 , Ellen Arruda 2 , Anthony Waas 6 , Nicholas Kotov 1 3 4
1 Chemical Engineering Department, University of Michigan, Ann Arbor, Michigan, United States, 2 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 5 Chemical Engineering, Hanyang University, Ansan, Kyounggi-Do, Korea (the Republic of), 6 Aerospace Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract10:30 AM - BB1.5
Hierarchical Biomimetic Design of Artificial Muscle Hydrogels.
Megan O'Grady 1 , Po-Ling Kuo 1 , Kit Parker 1
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show Abstract Electroactuated polymer hydrogels are promising materials for biological applications, namely because they can operate in physiological solutions at near neutral pH, require low voltages for actuation (1-5 V), are biocompatible, flexible, and can be easily fabricated. Although hydrogels and conductive polymers have been utilized extensively for artificial muscle applications, previous polymer constructs are not engineered to mimic structural and functional aspects of real biological muscle. However, by recapitulating the biological architectures which facilitate contraction in striated muscle, the timescale and magnitude of hydrogel contraction can be greatly improved. We have implemented a hierarchical biomimetic design to significantly enhance the bending of electroactuated hydrogels. In order to decrease Na+ diffusion time, an emulsion polymerization is utilized to create porous hydrogels. These hydrogels display increased bending angles (60-70 degrees) and faster electroactuation than those reported in the literature, demonstrating the importance of optimizing Na+ diffusion to increase hydrogel contraction. In addition, we have arranged the hydrogel into anisotropic patterns at multiple spatial scales (25μm – 5 mm), which can improve hydrogel contraction by controlling the spatial extent of ion diffusion within the polymer milieu. In effect, utilizing a photolithographic technique, we have developed a method to repeatedly and reliably arrange hydrogel architectures at the micro- and macroscale, as well as engineer structural gradients in hydrogels. Overall, our research highlights the need to replicate the multiscale contractile machinery of biological muscle in soft actuator systems. In addition, we have shown that these hydrogels can be used as fast synthetic actuators by toggling the magnitude and polarity of voltage applied in a physiological saline solution. Our results indicate that the actuation of biocompatible, polyelectrolyte hydrogels that can be significantly enhanced by capturing the contractile mechanisms of intact muscle tissue. These hydrogels represent a biocompatible, flexible polymer with rapid, reversible electroactuation in near neutral pH environments, which can be exploited for soft actuator applications in physiological environments.
10:45 AM - BB1.6
Haloform Adsorption on Crystalline Copolymers of Vinylidene Fluoride with Trifluoroethylene.
Carolina Ilie 1 , Jie Xiao 2 , Peter Dowben 2
1 Physics, SUNY Oswego, Oswego, New York, United States, 2 Physics , University of Nebraska at Lincoln, Lincoln, Nebraska, United States
Show AbstractReversible bromoform absorption on crystalline polyvinylidene fluoride with 30% of trifluoroethylene, P(VDF-TrFE 70:30) was examined by photoemission and inverse photoemission. The adsorption of bromoform on this polymer surface is associative and reversible. Molecular bromoform adsorption appears to be an activated process at 120 K with enhanced adsorption following the initial adsorption of bromoform. Strong intermolecular interactions are also implicated in the presence of a weak shake off or screened photoemission final state, whose intensity scales with the unscreened photoemission final state.
11:30 AM - BB1.7
Giant Electrocaloric Effect in Ferroelectric Polymers Near Room Temperature.
Bret Neese 1 3 , Baojin Chu 1 3 , Sheng-Guo Lu 1 , Yong Wang 2 , Eugene Furman 1 , Qiming Zhang 1 2
1 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, United States, 3 Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Electrical Engineering Department, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractWhen an electric field is applied to a dielectric material, it will induce a change in its polarization. The consequent changes in the entropy and temperature in the material are referred to as the electrocaloric effect (ECE), which can provide an efficient means to realize solid state cooling devices for a broad range of applications such as on-chip cooling and temperature regulations for sensors and electronic devices. Most research on the ECE focuses on ferroelectric ceramics, in which the polarization mechanism is ionic and temperature and entropy changes are typically too low to be of practical use. Applying an electric field to a polar polymer may induce a large change in the dipolar ordering resulting in a larger entropy change than that associated with ionic displacement in ceramics. Based on D-E loop measurements at varying temperature and using the Maxwell relation between the pyroelectric coefficient and electrocaloric effect (ECE), it is shown that a large ECE can be realized in the ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer at temperatures above the ferroelectric-paraelectric transition (above 70 ○C). A giant isothermal entropy change (>55 J/kgK) and adiabatic temperature change (> 12 ○C) are observed that are comparable with the giant magnetocaloric effect (MCE) materials. We further show that a similar level of ECE near room temperature can be achieved by working with the relaxor ferroelectric polymer of P(VDF-TrFE-CFE) (CFE: chlorofluoroethylene). The data also reveal that there is a difference in the temperature dependence of ΔS and ΔT between the two classes of ferroelectric polymer systems. That is, the normal ferroelectric P(VDF-TrFE) copolymer displays a decrease of both ΔS and ΔT with temperature at above the F-P transition, whereas in the relaxor ferroelectric P(VDF-TrFE-CFE), both ΔS and ΔT increases with temperature at above the dielectric constant peak in the experiment range investigated. The results presented indicate the potential of polar polymers in achieving high ECE because of the large entropy change associated with the electric field induced dipole ordering-disordering (O-D) process at temperatures near the O-D transformations.
11:45 AM - BB1.8
In-situ Synthesis of Metal Nanoparticles Embedded PDMS Composite Films.
Anubha Goyal 1 , Ashavani Kumar 1 , Pulickel M. Ajayan 1
1 Mechanical Engineering & Materials Science, Rice University, Houston , Texas, United States
Show Abstract12:00 PM - BB1.9
Application of a Chemically Adsorbed Monomolecular Layer for Increasing the Adhesion Force between Plated Copper Metal and the Resin Substrate.
Yuji Ohkubo 1 , Shogo Ohnishi 1 , Hiroyuki Yamamoto 1 , Kazufumi Ogawa 1 , Satoshi Miyazawa 2 , Kazuhiro Soejima 2 , Akira Nakano 2
1 Engineering, Kagawa university, Takamatsu, Kagawa, Japan, 2 Business development hq process technology dvlpmt.Center, Alps Electric Co., Ltd., Sendai, Miyagi, Japan
Show Abstract A chemically adsorbed monomolecular layer containing pyrrolyl group (PNN- CAM) was prepared between a plated copper layer and a resin substrate for increasing the adhesion force without roughening a surface of the resin substrate. Although it was not enough to increase the adhesion force between the copper layer and the resin substrate by using only PNN- CAM, the sufficient adhesion force was obtained by preparing a poly-pyrrole thin film between the copper layer and PNN-CAM. The measurements of the film thickness with an ellipsometer, the water contact angles with an automatic contact angle meter, IR spectra with a Fourier Transfer Infrared (FT-IR) spectrophotometer and UV-vis spectra with a ultraviolet-visible (UV-vis) spectrophotometer were performed for characterizing PNN-CAM and the poly-pyrrole thin film on the substrate. Auger Electron Spectroscopy (AES) was also applied in order to analyze the condition of the poly-pyrrole thin film between the resin substrate and the copper layer. The peel strength test was performed in order to evaluate the adhesion force. The best adhesion force was 0.98 [mN/m], and the targeted value 0.60 [mN/m] was sufficiently achieved.
12:15 PM - BB1.10
Copying the Natural Skeletal Muscle Design into a New Artificial Muscle System.
Maria Bassil 1 2 , Michael Ibrahim 1 , Mario El Tahchi 1 , Joseph Farah 1 , Joel Davenas 2
1 Department of Physics, Lebanese University -Faculty of Sciences II, Fanar, Jdeidet, Lebanon, 2 Laboratoire des Matériaux Polymères et des Biomatériaux, Claude Bernard University -Lyon I, Lyon, Villeurbanne, France
Show AbstractPolyacrylamide (PAAm) is an electroactif biocompatible non biodegradable material; they cannot be absorbed into tissues and cells due to their high molecular weight which make them the most promising candidate for many bio-applications such as implant and artificial muscle[1-2]. The key to exploitation of gels is the design of the system in which they are used. So mimicking the natural skeletal muscle need to create a new design that can regroup the electrical sensitivity, the linear displacement and the fast response while keeping a good mechanical properties [3]. Therefore achieving these goals using a simple low cost and relatively easy to process method is the key to make a real great progress.In this study a new design of an artificial muscle based on hydrolyzed PAAm gel is developed in order to be synthesized using an easy to process method, based on the advantage of fibrous systems and on the linear displacement actuation. This structure converts the electric energy into a linear displacement; it is able to receive electrical information and quickly transmit specific contraction responses.The model consists on a fiber like elements of hydrolyzed PAAM, working in parallel, embedded in a thin conducting gel layer which plays the role of electrodes. Fibers are encapsulated in a braided structure by disposing a thin elastic conductive gel film. The thin film holds the fibers together allowing them to act in parallel while keeping the speed of response, distribute forces to minimize damage of the fibers and provide a conduit for electricity in order to stimulate the fibers. The film deposited in the longitudinal section of fibers is connected to the negative electrode while the film deposited in the cross-section of fibers is connected to the positive electrode. Under an electrical stimulation the fibers contract linearly. Like in natural muscle, as the stimulation increases, the number of fiber in state of contraction increases and the strength of contraction of the whole muscle also increases.Further studies have to be made in order to improve the model efficiency.[1] Y.Osada and JP.Gong (1998) Advanced Materials 10 827 – 837.[2] Y.Bar-Cohen (2001) Electroactive Polymer (EAP) Actuators as Artificial Muscles: Reality, Potential, and Challenges Second Edition, Y.Bar-Cohen, Bellingham, SPIE Press Monograph Vol. PM136.[3] R.Bonser, W.Harwin, W.Hayes, G.Jeronimidis, G.Mitchell and C.Santulli (2004) Final Report, EAP-Based Artificial Muscles as an Alternative to Space Mechanisms ESA/ESTEC Contract No 18151/04/NL/MV.
BB2: Device Application
Session Chairs
Siegfried Bauer
Qibing Pei
Tuesday PM, December 02, 2008
Grand Ballroom (Sheraton)
2:30 PM - **BB2.1
Large Deformation and Instability in Electroactive Polymers.
Zhigang Suo 1
1 School of Engineering and Applied Sciences, Harvard, Cambridge, Massachusetts, United States
Show AbstractSubject to a voltage, a layer of a dielectric elastomer reduces its thickness, so that the voltage induces a high electric field. The positive feedback may cause the elastomer to thin down drastically, resulting in electrical breakdown. Furthermore, a recent experiment has shown that the homogeneous deformation of the layer can be unstable, giving way to an inhomogeneous deformation, such that regions of two kinds coexist in the layer, one being flat and the other wrinkled. We show that the free-energy function of a dielectric elastomer is typically non-convex, causing the elastomer to undergo a discontinuous transition from a thick state to a thin state. When the two states coexist in the elastomer, a region of the thin state has a large area, and wrinkles when constrained by nearby regions of the thick state. We also show that the instability can be tuned by the density of cross links and the state of stress.1. Zhigang Suo, Xuanhe Zhao and William H. Greene, A nonlinear field theory of deformable dielectrics. Journal of the Mechanics and Physics of Solids 56, 467-486 (2008).2. Xuanhe Zhao, Wei Hong and Zhigang Suo, Electromechanical coexistent states and hysteresis in dielectric elastomers. Physical Review B 76, 134113 (2007).3. Xuanhe Zhao, Z. Suo, Method to analyze electromechanical stability of dielectric elastomers. Applied Physics Letters 91, 061921 (2007).
3:00 PM - BB2.2
Growth and Characterization of Polymer Based Dielectrics Thin Films and their Application to Si and GaAs MOS Devices.
El Hassane Oulachgar 1 , Cetin Aktik 1 , Mihai Scarlete 2
1 Department of Electrical & Computer Engineering, Sherbrooke University, Sherbrooke, Quebec, Canada, 2 Department of Chemisty, Bishop's University, Sherbrooke, Quebec, Canada
Show Abstract3:15 PM - BB2.3
Development Of Conductive Polymer Single Layer Cantilever For Conductivity Measurement.
Ping Du 1 , Xi Lin 1 , Xin Zhang 1
1 Manufacturing Engineering, Boston University, Brookline, Massachusetts, United States
Show AbstractConductive polymers are an unusual class of organic materials that exhibit some reduction or oxidation (redox) state dependent properties. In this work, we focus on the actuator aspect, where the volume change relies on the ions and solvent flux.Polypyrrole is synthesized electrochemically in a typical three-electrode set up. The synthesis is carried on in 0.1 M pyrrole monomer and 0.1 M sodium dodecylbenzene sulfonate (NaDBS) aqueous solution, and controlled by constant current density of 1 mA/cm2 and 0.5 mA/cm2, respectively. The 1 mA/cm2 current density results in higher and unstable potential which might overoxidize the polymer and create inferior structure, while 0.5 mA/cm2 current density gives very stable potential and not exceed 0.7 V. The following syntheses are all conducted in this value. We further examine the relationship between the polymer thickness and the consumed charge density by varying the synthesis time, from 1 min to 30 min. Exclude the first sample which synthesized in the beginning, all following samples fit very well into a linear manner. Based on this information, we can precisely control the desired polymer thickness simply by adjusting the current density and deposition time.For the micro actuator design, we use two different approaches by standard microfabrication techniques. The bilayer cantilever is similar as Smela’s, using different adhesion method. The anchor part consists of Cr and Au, while the moving part is barely Au on top of glass. Then we apply the sacrificial method for single layer cantilever. Because Ti etchant (typically hydrochloric acid) will attack Cr as well, the under etching of Ti will make the whole structure peeled off from substrate. Therefore we use Au as the sacrificial layer and Ti as the anchor. During the synthesis, polypyrrole first deposit on Au layer, and extend to Ti layer after sufficient time. When the deposition complete, we can easily under etch the Au to release the cantilever, leaving only polypyrrole as the moving part. Without the bending of bilayer, we hope this structure could be used as a linear actuator in future.We also characterize the polypyrrole films by measuring its conductivity in dry state using four point probe station. First we measure the polypyrrole and Au bilayer cantilever. The conductivity ranges from 559 to 1898 S/cm, which can be compared to the value report by other people. While the resistivity is near proportional to thickness, which means the sheet resistance is almost constant. One possible reason could be that the probes may penetrate the polymer so the conductivity is measured from both polymer and gold. So we try to do further measurement by using our single layer cantilever. The preliminary result shows the a series of seven cantilevers synthesized for 10 min have average thickness of 3.0 μm, and the conductivity is very consistent with a average of 5.4 S/cm and standard deviation of 0.0875.
4:00 PM - BB2.4
Composite Electromagnetic Wave Absorber Made of Aluminum Particles or Sendust Particles Dispersed in Polystyrene Medium.
Kenji Sakai 1 , Yoichi Wada 1 , Yuuki Sato 1 , Shinzo Yoshikado 1
1 Electronics, Doshisha University, Kyotanabe, Kyoto, Japan
Show Abstract4:15 PM - BB2.5
Changes in Morphology and Electrical Properties of Annealed PEDOT:PSS Layers and Their Influence on the Performance of Polymer Blend Photodetectors.
Bettina Friedel 1 , Panagiotis Keivanidis 2 , Neil Greenham 1
1 Physics, University of Cambridge, Cambridge United Kingdom, 2 Physics, Imperial College London, London United Kingdom
Show AbstractThe conducting polymer poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is commonly used as an electrode material in organic photovoltaic devices. It modifies the energy barrier at the hole-collecting electrode, and it also smoothes the relatively rough ITO surface, reducing short circuits. PEDOT:PSS is usually deposited from an aqueous colloidal solution, wherein the colloidal particles consist of a PEDOT-rich core, surrounded by a more insulating PSS shell. The morphology of the deposited PEDOT:PSS film can be modified by annealing, and since PEDOT:PSS is infusible, the temperature limit is set to the onset of degradation at around 350degC. The densification which occurs upon annealing, together with the modification of the PSS shell allows adjustment of the conductivity and workfunction. Here, we demonstrate the effects of PEDOT:PSS annealing in photodetecting devices based on blends of poly(3-alkylthiophenes) with the polyfluorene copolymer poly(9,9-dioctyl-fluorene-co-4,7-di-thiophen-2-yl-benzothiadiazole) (F8TBT). We present AFM and SEM results on morphological changes of the PEDOT:PSS colloidal particles due to different annealing temperatures and the influence on film density. We show how annealing modifies the electrical properties of the film, allowing the overall device performance to be improved.
4:30 PM - BB2.6
Optimization of New Ultralow-k Materials for Advanced Interconnection.
Xuan Li 1 , James Economy * 1
1 Materials Science and Engineering , University of Illinois at Urbana-Champaign, Urbana , Illinois, United States
Show AbstractThe demand for increased signal transmission speed and device density for the next generation of multilevel integrated circuits has placed stringent demands on materials performance. Currently, integration of the ultra low-k materials in dual Damascene requires chemical mechanical polishing (CMP) to planarize the copper. Unfortunately, none of the commercially proposed dielectric candidates display the desired mechanical and thermal properties for successful CMP. A new polydiacetylene thermosetting polymer (PDEB-TEB) which displays a low dielectric constant (low-k) of 2.7 was recently developed. This novel material appears to offer the only avenue for designing an ultra low k dielectric (1.85k), which can still display the desired modulus (7.7Gpa) and hardness (2.0Gpa) sufficient to withstand the process of CMP. In this talk, we will present recent additional studies to further characterize the thermal properties of spin-on PDEB-TEB ultra-thin film. These include the coefficient of thermal expansion (CTE), biaxial thermal stress, and thermal conductivity. Thus the CTE is 2.0*10^-5K^-1 in the perpendicular direction and 8.0*10^-6K^-1in the planar direction. The low CTE provides a better match to the Si substrate which minimizes interfacial stress and greatly enhances the reliability of the microprocessors. Initial experiments with oxygen plasma etching suggest a high probability of success for achieving vertical profiles.
4:45 PM - BB2.7
Investigating A Few Key Issues of Ionomeric Polymer/Conductive Network Composite Electromechanical Transducers.
Sheng Liu 1 2 , Minren Lin 2 , Wenjuan Liu 3 , Ralph Colby 3 2 , Qiming Zhang 1 2
1 Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, United States, 3 Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractWe investigate ionomeric polymer/conductive network composite (IPCNC) electromechanical transducers, in which the ions moving in and out of the IPCNC generate electromechanical transduction. We especially investigate a few issues which are crucial to realize high performance IPCNC transducers, i.e., development of extensional actuators and raising the electric field level in the device while keeping the applied voltage below one or two volts. It is noted that while the applied voltage is limited to below the electrochemical reaction threshold, there is no limit on the electric field level allowed in the composites, which can be increased markedly by working with thin composites and developing multilayer actuators. It is further demonstrated that the device speed is proportional to 1/d^2, where d is the individual layer thickness, and hence the actuator speed and efficiency can be improved significantly in thin layer actuators. In addition, by properly choosing the ionic liquid with optimized ion sizes, the actuator efficiency can be further improved.
5:00 PM - BB2.8
Tuning Threshold Voltage and Off Current in Organic Transistors by Precharging Gate Dielectrics with Electron Microscope and Corona Sources.
Howard Katz 1 , Kedar Deshmukh 1 , James West 2
1 Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 2 Electrical Engineering and Computer Science, Johns Hopkins University, Baltimore, Maryland, United States
Show AbstractFor plastic electronics applications, it is necessary in some cases to ensure consistent transistor switching voltages throughout a circuit, and in other cases it is desirable to produce controlled but contrasting switching voltages among transistors with the same materials and dimensions. We perform corona charging of gate dielectrics, especially polymers such as CYTOP® (a heavily fluorinated polymer) and poly(methyl methacrylate), prior to completing field effect transistor fabrication using thiophene oligomer and polymer semiconductors. This results in threshold voltage shifts and off-current increases, from a combination of static charging and surface reactions. Static charging is assessed by Kelvin probe measurements and surface reactions are evident by changes in contact angles and photoelectron spectra. We further found that a scanning electron microscope source serves as a novel, regiodefined, and chemically cleaner tool for carrying out the charging of gate dielectric polymers, again prior to deposition of the semiconductor and source-drain contacts. Shifts of tens of volts, on the same order as the threshold voltage shifts, with no deleterious change in off current or mobility are observed. Surface analyses reveal that morphology and surface functionality are maintained. Contrasting transistors can be fabricated just millimeters apart, differing only in proximity to the charging source during the charging process. Translation of this method to printed organic circuitry will be discussed.
5:15 PM - BB2.9
Micropatterning of a Photocurable Hydrogel in a Microfluidic System.
Huijie Hou 1 , Arum Han 1
1 Electrical and Computer Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractThermoresponsive hydrogels such as poly(N-isopropylacrylamide) (PNIPAAm) that can swell and deswell under external stimulus are attractive materials for applications such as cell release in tissue engineering, actuation of miniaturized components, and active controlling of surface properties. Micropatterned hydrogels show improved thermoresponsiveness compared to bulk hydrogels. Microfabricated hydrogel structures have been integrated into various miniaturized systems such as cell arrays or as actuation mechanisms. Current methods of hydrogel micropatterning are either through the use of photopolymerization combined with a photolithography mask or require sophisticated fabrication steps and equipments. Direct photopolymerization is a simple micropatterning method but generating high density arrays of hydrogel microstructures are challenging. Hydrogel microstructures with short distances tend to be connected to each other due to UV light scattering during photopolymerization. Hydrogel microstructures smaller than few tens of micrometers are also challenging to make due to their poor adhesion to substrates that results in micropillar detachment from substrates during the uncured hydrogel washing step. The softness and weak mechanical strength of most hydrogels make small microstructure formation even more challenging. We present here a method for fabricating several micrometer scale microstructures with high density and large area coverage using a maskless photopolymerization method combined with hydrophilically patterned hydrophobic substrates. Photoresist was first patterned to form the microstructure arrays (diameters: 15 μm ~ 200 μm, separations: 0 μm ~ 200 μm) on a glass substrate and then treated by trichlorosilane to make the area not covered by the photoresist patterns hydrophobic. The photoresist patterns were then removed in acetone, resulting in a hydrophobic substrate with arrays of hydrophilic spots. Microfluidic channel arrays made of poly (dimethyl siloxane) was placed on the substrate covering the hydrophilic spots, PNIPAAm injected into the microchannels, followed by flushing out the prepolymer hydrogel solutions at a controlled flow rate using a syringe pump. The hydrogel prepolymer solution remained only at the hydrophilic spots due to the surface tension and was subsequently cured under an UV light. Features down to 5 μm in diameter were successfully patterned to fully cover a 4 cm X 5 cm area with PNIPAAm micropillar arrays. Feature sizes could be controlled by adjusting the flushing speed of PNIPAAm pre-polymer solution and channel height of the microchannels. The developed method provides a simple and easy way of creating high density thermoresponsive hydrogel microstructure arrays covering a large surface and can be used to control the thermoresponsiveness and surface properties of such a surface.
5:30 PM - BB2.10
On the DC Breakdown Mechanism of P(VDF-HFP) Capacitor Films with High Electrical Energy Density.
Xin Zhou 1 , Shihai Zhang 1 , Qin Chen 1 , Yong Wang 1 , Chen Zou 1 , Qiming Zhang 1
1 Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractPolarpolymers with high dipole density have the potential to achieve very high electric energy density Ue, required in many modern electronics and electric systems. We demonstrate that by combining the nonpolar to polar molecular structure changes, a very high Ue (>25 J/cm3) can be obtained in defects modified poly(vinylidene fluoride) polymers, such as P(VDF-CTFE) (CTFE: chlorotrifluoroethylene), and P(VDF-HFP) (HFP: hexafluoropropylene). In this study, the DC breakdown mechanism of P(VDF-HFP) capacitor film was investigated systematically over a wide range of film thickness, temperature, and voltage ramp rate. It was found that above room temperature the DC breakdown strength decreases with temperature while below room temperature, it is nearly a constant. At room temperature, the DC breakdown strength increases with voltage ramp rate and but does not depend on the film thickness. The experimental results and theoretical simulation suggest that different breakdown mechanisms may be dominant at different temperature regions.
5:45 PM - BB2.11
Earthworm Inspired Locomotion from Thermoresponsive Organic-Inorganic Hybrid Hydrogels.
Hitesh Arora 1 2 , Rahul Malik 1 , Lilit Yeghiazarian 3 , Claude Cohen 2 , Ulrich Wiesner 1
1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 School of Chemical and Biomolecular Engineering, Cornell University, Ithaca , New York, United States, 3 Biological Engineering, UCLA, Los Angeles, California, United States
Show AbstractTransformation of energy into directed motion requires different forms of complexity at different length scales. Nature demonstrates several mechanisms for inducing motion, at different length scales, through various organisms. It is desirable to mimic these natural systems to make efficient devices for MEMS and microfluidics. Although devices based on biological systems have demonstrated that directed motion can be induced using ATP powered biomolecules such as motor proteins, the stringent physiological conditions required limit the applicability of such systems. In contrast, a synthetic material may provide the necessary robustness and freedom to tune parameters as per the requirements. Responsive materials such as polymer hydrogels are ideal for such a device. The responsive nature has been exploited in the past to make devices for applications ranging from drug delivery to micro-valves.Previously, we developed a prototype device based on thermoresponsive hydrogels that mimics the earthworm locomotion. The mechanism involves shrinking and swelling small segments of a long gel, induced by volume phase transition through a simple temperature stimulus using peltier elements, an effect generated in the earthworm by flexing and stretching of muscles along the body. The shrinking segments moves the body forward while swollen segments hold the surface to prevent the moving body from slipping. The device, capable of generating directed motion at velocities of order 10 µm/sec and cargo carrying capability, had some limitations pertaining to mechanical robustness, long ionization times to induce large volume changes, slow swelling kinetics and slippage leading to imperfect motion. Here we show a new device, based on the same working principle, which overcomes these challenges. The device is made of super-porous, organic-inorganic hybrid hydrogels that show large volume phase transitions above 32°C without requiring additional ionization and show fast swelling kinetics that allow the gels to come back to their initial size in short times. With these gels, confined in rough capillary walls, we were able to generate efficient slip-free motion, over multiple cycles and with velocities of order µm/sec. In comparison, one of the fastest crawling eukaryotes, Amoebae of Acrasis (with cell surface area of 759 µm2), moves with an average speed of 71.6 µm/min. Since the time scale for shrinking and swelling decreases as the critical dimension of the gel becomes smaller, the velocity of gel motion is expected to increase dramatically by decreasing the diameter of the gel. We anticipate that the principle described herein might be widely utilized in a variety of areas in biotechnology, microfluidics, small-scale robotics and drug delivery.
Symposium Organizers
Zhongyang Cheng Auburn University
Qiming Zhang The Pennsylvania State University
Siegfried Bauer Johannes-Kepler University Linz
Debra A. Wrobleski Los Alamos National Laboratory
BB3: New Materials and Characterization
Session Chairs
Wednesday AM, December 03, 2008
Grand Ballroom (Sheraton)
9:00 AM - **BB3.1
Multiferroic Magnetoelectric Polymer-Based Composites.
Ce-Wen Nan 1
1 Materials Science & Engineering, Tsinghua University, Beijing China
Show Abstract9:30 AM - BB3.2
Ferroic Nanofiber Yarns for Nanofluidic Applications.
Kostya Kornev 1 , Taras Andrukh 1 , Igor Luzinov 1
1 School of Materials Science & Engineering, Clemson University, Clemson, South Carolina, United States
Show AbstractMagnetic nanofilaments are making recent publications; described as long flexible chains made of magnetic colloids and linkers, these particles have already been used in self-propulsion of bodily cells and DNA. Typically, diameter of these filaments is measured in nanometers, hence their applications are limited to nanomechanical systems. The major barrier to fabricate microscopic magnetic or ferroelectric filaments is that the flexural rigidity and magnetization/polarization cannot achieve high values simultaneously. In this paper, we discuss new approach which avoids these problems. Highly porous (~ 83%) polyvinylidene difluoride (PVDF) / polyethylene oxide (PEO) nanofibers of about 50-500 nm in diameter were prepared by electrospinning. Wetting experiments and theoretical analysis suggest that nanofibers have a core-skin morphology (PEO as a core and PVDF as a skin). Assembling these nanofibers in the yarns, we produce materials with high tenacity, which can be bent, knotted, or twisted without any breakage. Results of DSC, TGA, and FTIR characterization of the produced yarns reveal the presence of crystalline PVDF β-phase responsible for ferroelectric properties of the material. These yarns can be made magnetic by impregnating them with magnetic nanoparticles. Since the yarns are very flexible and field responsive, they can be irreversibly bent and twisted. A series of experiments show that ferroic yarns can be used as conduits and collectors in nanofluidic devices. Probing aerosol droplets, biofluids from capillaries, making operations on single cells, are only a few applications under consideration.
9:45 AM - BB3.3
Low Loss Magnetodielectric Polymer Nanoparticle Composites for Radio Frequency (RF) Applications.
Ta-I Yang 1 , Leo Kempel 2 , Peter Kofinas 3
1 Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland, United States, 2 Department of Electrical and Computer Engineering, Michigan State University, East Lansing, Michigan, United States, 3 Fischell Department of Bioengineering, University of Maryland, College Park, Maryland, United States
Show AbstractThe aim of this research is to develop polymer nanocomposites with improved dielectric permittivity (ε), magnetic permeability (μ), and low energy loss at radio frequencies. Surfactant-modified iron oxide and nickel zinc ferrite nanoparticles of various sizes were successfully synthesized by a seed-mediated growth method. The free precursor ions present during synthesis is the major factor contributing to the growth of larger particles. The dielectric permittivity and magnetic permeability of the resultant block copolymer (styrene-b-ethylene/butylene-b-styrene) nanoparticle composites increased with increasing amount of doped nanoparticles. However, the magnetic permeability of the composites was significantly influenced by the size of the doped nanoparticles. The optimum size range for magneto-dielectric particles to obtain high magnetic permeability is between 30 and 100 nm, where single domain ferromagnetic particles without any domain walls are present. Polymer nanoparticle composites using softer nickel zinc ferrite nanoparticles exhibited higher magnetic permeability (μ=2) with lower dielectric loss tangent (tan δ<0.01) at 1 GHz.
10:00 AM - BB3.4
Polyaniline Nanostructures for Hydrogen Storage Applications.
Sesha Srinivasan 1 , Michael Jurczyk 1 , Ayala Phani 2 , Ashok Kumar 1 , Yogi Goswami 1 , Elias Stefanakos 1
1 , University of South Florida, Tampa, Florida, United States, 2 , NANO-RAM Technologies, Bangalore India
Show AbstractPolyaniline nanostructures such as nanofibers and nanospheres have been synthesized using chemical templating and electrospun techniques in presence of surfactants as dopants. The reversible hydrogen sorption characteristics namely kinetics, pressure-composition isotherms and life-cycle measurements were performed on these polyaniline (PANI) nanostructures at high hydrogen pressures and room temperatures. The rapid uptake and release of hydrogen (~95% of hydrogen uptake in less than 10 minutes) was observed and this may be due to the unique nanostructures of polyaniline fabricated in the present study. The structural, microstructural, chemical and optical characterizations were compared and correlated with the observed hydrogen sorption behavior in these polyaniline nanostructures.
10:15 AM - BB3.5
Pattern Transformation in Periodic, Porous, Elasto-plastic Microstructures.
Srikanth Singamaneni 1 , Katia Bertoldi 2 , Sehoon Chang 1 , Ji-hyun Jang 3 , Edwin Thomas 3 , Mary Boyce 2 , Vladimir Tsukruk 1
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Department of Materials Science and Engineering and Institute of Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractSingle and multi-component periodic porous micro and nanostructures have attracted increased attention over the last two decades owing to their current and prospective applications in photolithography, photonics, phononics, microfluidics, sensors, and scaffolding. When these microstructures are stressed, their periodic porous geometry can suddenly change at a critical point due to mechanical instability of the structural elements leading to dramatic reorganization of organized microstructures. We present the recent observation of the sudden transformation of periodic microporous structures of a crosslinked epoxy-based Novolak photoresist fabricated by interference lithography. The mechanical instability is brought about by polymerization of acrylic acid onto the porous microframe structures. The results of a numerical investigation confirm the critical role of the compressive stresses developed in the microframe structure. In striking contrast to the earlier observations of elastic instabilities in porous elastomeric structures, the elastic-plastic nature of the crosslinked microstructure studied here provides the ability to dramatically transform the original geometry and lock in the new pattern.
10:30 AM - BB3.6
Operation Characteristics of Ionic Polymer-Metal Composite using Ionic Liquids.
Kunitomo Kikuchi 1 , Masafumi Miwa 2 , Shigeki Tsuchitani 3
1 Graduate School of Systems Engineering, Wakayama University, Wakayama-shi Japan, 2 Institute of Technology and Science, The University of Tokushima, Tokushikma-shi Japan, 3 Department of Opto-Mechatronics, Faculty of Systems Engineering, Wakayama University, Wakayama-shi Japan
Show Abstract Recently, it was reported that Nafion-based ionic polymer-metal composite (IPMC) using ionic liquids (ILs) could operate in air. In this study, we evaluated operation of IPMCs using 1-ethyl-3-methyl-imidazolium tetrafluoroborate (EMIBF4), 1-buthyl-3-methyl-imidazolium tetrafluoroborate (BMIBF4), and 1-buthyl-3-methyl-imidazolium hexafluorophosphate (BMIPF6) as ionic liquids. Among IPMCs using three kinds of ILs, IPMC using BMIPF6 had the largest displacement in air under an application of a rectangle waveform voltage (±2.0V) with a frequency of 0.5Hz. Compared with the previously reported Flemion®-based IPMC using BMIBF4[1], Nafion®-based IPMC using BMIBF4 exhibited a curvature of 0.6m-1, which was approximately a half of that of the Flemion®-based IPMC (1.5m-1). On the other hand, the curvature of Nafion®-based IPMC using BMIPF6 was almost same as that of Flemion®-base IPMC using BMIBF4. In the previous study concerning Flemion®-based IPMC, the one using BMIBF4 had larger displacement than that using BMIPF6. This difference of the performance between Nafion®-based and Flemion®-based IPMCs using the same kinds of ILs might be based on difference in molecular structure and electrical affinity to ILs of the both ion exchange materials. We found that the behavior of IPMC using ILs changed depending on environmental humidity. In all evaluating conditions, slope of response curves at initial stage (the initial response speed) increased with increase in humidity and the applied voltage. Increase in the initial response speed at higher humidity and higher applied voltage, is probably due to increase in moving speed of counter ions in IPMC in these conditions. It is thought that mobility of counter ions in IPMC increased with increasing humidity. To estimate equivalent circuit of IPMC using ILs and to investigate influences of the derived circuit parameters on the operation of IPMC, we evaluated frequency dependence of complex impedance of IPMC. Complex impedance plane plots (Cole-Cole plots) of IPMC were preferred at higher frequencies over 5.0Hz. In all measurement conditions, the complex impedances were plotted in semicircular shape. This result might indicate that the equivalent circuit of IPMC is expressed by a parallel combination of resistance element and capacitance element in this frequency range. The curvature of IPMC using IL was larger than that of IPMC having lower resistance element. The value of resistance element of IPMC decreased with increase in environmental humidity. This means that ionic conductivity of the Nafion® membrane increased with increasing environmental humidity. It is thought that the increase in ionic conductivity at higher humidity resulted in the increase in the initial response speed, as described in above. This work was supported in part by Grant-in-Aid for Scientific Research C (No. 18560249) from Japan Society for the Promotion of Science (JSPS).[1] J. Wang et al., Proc. SPIE, Vol. 6168, 61680R (2006)
10:45 AM - BB3.7
α to β Phase Transformation in Nanocomposites of Poly (Vinylidene Fluoride) Doped with Silver Nanoparticles.
Daniel Miranda 1 , Vitor Sencadas 1 , Ana Sanchez-Iglesias 2 , Isabel Pastoriza-Santos 2 , Luis Liz-Marzan 2 , Jose Gomez Ribelles 3 4 5 , Senentxu Lanceros-Mendez 1
1 Departamento de Física, Universidade do Minho, Braga Portugal, 2 Dept. de Química Física, Universidade de Vigo, Vigo Spain, 3 3Centro de Biomateriales, Universidad Politécnica de Valencia, Valencia Spain, 4 Regenerative Medicine Unit, Centro de Investigación Príncipe Felipe, Valencia Spain, 5 , 5CIBER en Bioingeniería, Biomateriales y Nanomedicina, Valencia Spain
Show Abstract11:30 AM - BB3.8
Enhanced Ferroelectric Properties of Electrospun Polyvinylidene difluoride-based Nanocomposites: Towards Multiferroic Materials.
Jennifer Andrew 1 , David Clarke 1
1 Materials, University of California- Santa Barbara, Santa Barbara, California, United States
Show AbstractMultiferroic materials exhibit both ferromagnetic and ferroelectric properties, which tend to be mutually exclusive in single-phase materials. Therefore, composite materials are the obvious approach to developing a material with both a high electric permittivity and high magnetic permeability. In composite systems the magnetoelectric effect arises from the mechanical coupling between magnetostrictive and piezoelectric phases. Magnetoelectric coupling in composite systems is an interfacial phenomenon. To enhance this coupling, the interfacial area between the two phases should be maximized. This can be accomplished using nanoparticles, which have a large surface area-to-volume ratio. Ceramic multilayer multiferroic materials are plagued with porosity and cracking at the interfaces between the two phases, resulting in reduced performance. To avoid the limitations of these ceramic composites, ferroelectric polymer- magnetic nanoparticle (PVDF-Ni0.5Zn0.5Fe2O4) composites with enhanced properties were prepared via electrospinning.
Polyvinylidene difluoride (PVDF) fibers with continuously dispersed ferrite (Ni0.5Zn0.5Fe2O4) nanoparticles were prepared by electrospinning from dimethyl formamide (DMF) solutions. The ferrite nanoparticles were synthesized using aqueous coprecipitation routes, and were subsequently functionalized with an organo-silane, forming stable ferrofluids in DMF. The effects of the electrospinning processing conditions and nanoparticle loading on the fiber morphology, crystallinity and the crystalline structure of PVDF were investigated. SQUID magnetometer and dielectric measurements were also performed to determine the materials’ magnetic and dielectric properties.
Electrospinning provides a simple one- step technique to form PVDF in the ferroelectric β- phase directly from solution. The average fiber diameter can be tuned from 150nm to 2 microns by adjusting the processing parameters. We have shown that the amount of β-phase can be enhanced by the addition of a well-dispersed nanoparticle phase. The fraction of β-phase increases with increased nanoparticle loading, with a maximum fraction of β- phase, F(β)max, of 1.
11:45 AM - BB3.9
``Smart" Surfaces of Polymer Brushes.
Dong Meng 1 , Qiang Wang 1
1 Chemical and Biological Engineering, Colorado State University, Fort Collins, Colorado, United States
Show Abstract12:00 PM - BB3.10
Dielectric Breakdown of Transformer Insulation Materials Under Cryogenic and Room Temperatures.
Horatio Rodrigo 1 , Danny Crook 1 , Steve Ranner 1 , Richard Liang 1 2 , Aniket Ingole 1 2
1 Center for Advanced Power Systems, Florida State University, Tallahassee, Florida, United States, 2 Industrial Engineering, Florida State University, Tallahassee, Florida, United States
Show AbstractThe results of breakdown voltage measurements on "ThermaVolt", a material used in power transformers is presented. The performance of this material is compared with others that consist of polymer resins that have been modified by the addition of nano-particles. The polymers are Epoxies with the addition of Barium Titanate and Alumina. The breakdown voltage measurements have been conducted under 60 Hz AC high voltage and high voltage impulse voltage with standard lightning waveform.The electrode configuration gives a uniform field with 25 mm diameter electrodes made of Stainless Steel with Bruce profile. Measurements presented are at room temperature 293 K and at Liquid Nirtogen temperature 77 K.
12:15 PM - BB3.11
Bilayer Microactuator of Two Kinds of Polypyrroles Doped with Different Dopants.
Shigeki Tsuchitani 1 , Kosei Chikatani 2 , Kunitomo Kikuchi 2
1 Department of Opto-Mechatronics, Wakayama University, Wakayama-shi Japan, 2 Graduate School of Systems Engineering, Wakayama University, Wakayama-shi Japan
Show AbstractMany applications of conjugated polymers as soft actuators are being proposed, since they have many excellent characteristics compared with conventional inorganic actuators, such as light weight, large deformation and low operation voltage. Recently, microactuators using conjugated polymers, which are fabricated by MEMS (Micro Electro Mechanical Systems) technology, are attracting much attention, aiming at realization of micro-valve, micro-pump, microrobot arm, etc.We fabricated a bilayer microactuator of two kinds of polypyrroles (PPys) doped with different dopants, i.e., dodecylbenzenesulfonic acid (DBS) and p-phenolsulfonic acid (PPS), on a silicon substrate using surface micro-machining technology. The fabricated actuator was 0.5mm long, 0.2mm wide and 1μm thick. It bended about 90 degree under an application voltage of 0.7V in an aqueous solution of sodium hexafluorophosphate (NaPF6).In the fabrication of the microactuator, a patterned chromium layer (thickness: 5nm), which had a function of an adhesion layer to fix the microactuator on the substrate, was formed on the silicon substrate at first. After that, a gold layer (thickness: 100nm) was deposited both on the chromium layer and the bear silicon substrate, and pattered to the shape of the microactuator. Then, PPy doped with PPS (PPy(PPS)) was deposited on the pattered gold layer potentiostatically in an aqueous solution of pyrrole (0.25M/l) and PPS (0.15M/l). Furthermore, PPy doped with DBS (PPy(DBS)) was successively deposited on the PPy(PPS) layer potentiostatically in an aqueous solution of pyrrole (0.25M/l) and DBS (0.15M/l).The fabricated microactuator was actuated in the aqueous solution of NaPF6 (1M/l) by applying a voltage of 0.7V between the gold layer and a counter electrode. In the first voltage application, the gold layer which constructed the microactuator, peeled away from the silicon substrate except the contacting part with the chromium layer and bent about 90 degree in about 18s, since adhesion force between gold and silicon is enough smaller than that between gold and chromium. After the second voltage application, the microactuator bent stably having a response speed of about 5s. Since the main components of the fabricated microactuator are two kinds of polypyrroles doped with the different dopants and the thickness of the gold layer was enough smaller than that of polypyrrole layers, the effects of ductility of the gold layer on the operation of the microactuator is very small. As a result, the stable operation of the microactuator is expected.
BB4: Device Application
Session Chairs
Wednesday PM, December 03, 2008
Grand Ballroom (Sheraton)
2:30 PM - **BB4.1
High Frequency Length Mode PVDF Behavior over Temperature.
Mitch Thompson 1 , Minoru Toda 1 , Melina Ciccarone 1
1 , Measurement Specialties, Inc, Wayne, Pennsylvania, United States
Show Abstract3:00 PM - **BB4.2
Models for Actuation, Failure and Tearing of Electroactive Polymers.
Robert McMeeking 1 , Salomon Jimenez 1
1 , University of California, Santa Barbara, California, United States
Show Abstract3:30 PM - BB4.3
Membrane Based High Performance Biosensor Platform.
Xu Lu 1 2 , Liling Fu 1 , Zhuo Xu 2 , Wei Ren 2 , Anxue Zhang 1 , Zhongyang Cheng 1
1 , Materials Research and Education Center, Auburn University, Auburn, Alabama, United States, 2 , Electronic Materials Research Laboratory, Xian Jiaotong University, Xi'an, Shaanxi, China
Show AbstractPiezoelectric membrane was recently introduced as a high performance platform for the development of biosensor. The sensor principle is based on the resonance frequency change. Therefore, determination of the resonance frequency is the key. In this paper, the fabrication and characterization of square membranes made of piezo-PVDF are reported. The thickness of the PVDF is about 25 microns, while the size of the membrane is from 2 mm to 6 mm. The resonance behavior of these membranes was characterized under different conditions: two sides with air in different pressure, one side in air and the other in liquid, two sides in liquid. In the experiments, the liquid with different viscosities and densities were utilized. It is experimentally found that the membrane based devices, working in the bend mode, could keep a nearly same Q value both in water and air and that the membrane exhibits a much higher mass sensitivity than cantilever based device, which make the piezoelectric membrane a stronger candidate for the developing sensor for in-situ detection. Furthermore, the influences of size, pressure and viscosity on the resonance frequency and the Q value are experimentally determined and the results are discussed.
4:15 PM - BB4.4
Colorimetric and Ratiometric Cu(II) Ion Sensors Based on Silica Nanoparticles with Multilayered Shells Doped with Ir(III)-Complex.
Hosub Kim 1 , Kookheon Char 1
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractCopper is the essential trace element in many biological processes, but it typically reveals toxicity at elevated concentration. For these reasons, there has been great interest to monitor Cu(II) ions in the last decades and many research groups designed and synthesized various kinds of chemosensors to detect Cu(II) ions with high sensitivity and selectivity. We demonstrate, in this presentation, water-soluble colorimetric and ratiometric Cu(II) ion sensors based on the selective quenching of phosphorescent emission in the shell region doped with Ir(III)-complexes. Silica nanoparticles embedded with green-emitting Ir(III)-complex in the core region were synthesized by the modified Stöber method and multilayer shell structures were prepared by the layer-by-layer deposition with positively charged red-emitting Ir(piq)2-PEI complexes and negatively charged CBZ-PAA. This core/shell type Cu(II) ion sensors show the emission color changes proportionally with the concentration of Cu(II) ions, thus these can be applied for naked eye detection and simple quantitative analysis of Cu(II) ions. Additionally, it has high sensitivity and selectivity for Cu(II) ions as well as reversibility or recyclability. The detection dynamic range, the concentration range for changing emission colors could be modulated by adjusting the number of bilayers in the multilayered shells.
4:30 PM - BB4.5
Controllable Growth and Mechanical Properties of Layer-by-Layer Assembled Multilayer Films using Different Deposition Methods.
Jinhwa Seo 1 , Raehyun Kim 2 , Yeongseon Jang 1 , Hyojin Lee 3 , Jongho Jeon 3 , Jwamin Nam 3 , Kookheon Char 1
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Hybrid Materials Research Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 3 Department of Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show AbstractThe Layer-by-Layer (LbL) deposition has been known to be one of simple and versatile methods to prepare functional multilayered films. To date, the mechanical properties of LbL assembled polyelectrolyte thin films have received much attention for their useful applications such as membranes, sensors, and many other devices. By varying the assembly parameters (i.e., pH or salt concentration of polyelectrolyte solution, environmental relative humidity, strong or weak charged electrolytes), the mechanical properties of polymer thin films can be controlled. In present study, we demonstrate that the different deposition methods of LbL assembly (i.e., spin vs. conventional dip method) has also effect on the film growth and mechanical properties of polyelectrolyte multilayer thin films based on the different assembly mechanism. Multilayer films based upon strong or weak electrostatic association between poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) have been prepared with various pH combinations using the dip and spin-assisted LbL methods and the Young’s modulus of dip- and spin-assisted LbL assembled PAH/PAA multilayer films is obtained by nanoindentation using a liquid atomic force microscope. We also investigate the effect of different modulus of polymer films in wet condition on various cell attachment and proliferation.
4:45 PM - BB4.6
Optimal Design of Responsive Gels for Actuators.
Xuanhe Zhao 1 , Wei Hong 1 2 , Zhigang Suo 1
1 School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Aerospace Engineering, Iowa State University, Ames, Iowa, United States
Show AbstractResponsive polymer gels have been extensively used for biological, thermal, and mechanical actuators. With the advantages of biocompatibility, high sensitivity, light weight and low cost, the responsive-gel-based actuators are replacing traditional actuators in microfluidic chips, drug-delivery devices, and biosensors. On the other hand, because the actuation of responsive gels usually involves high material nonlinearity and large deformation, there are very few models and design schemes for responsive-gel-based actuators. We developed a theory for large deformation of responsive gels, and implemented the theory into numerical codes. Using the codes, we developed various models of responsive-gel actuators in microfluidic chips, drug-delivery devices, and biosensors. The models were validated by comparing their predictions with available experimental data. Based on the modeling results, we showed that: 1) The response of an actuated gel is determined by both its properties (e.g. crosslink density, hydrophobicity et al) and mechanical constraints. 2) The swelling of a polymer gel can greatly reduce its shear modulus and cause anisotropy of its mechanical properties. 3) By varying a gel’s properties, mechanical constraints, and swelling ratio, one can reach an optimal design of responsive gels for actuators.
5:00 PM - BB4.7
Highly Selective Polythiophene/Nanotube Sensors.
Fei Wang 1 , Yong Yang 2 , Timothy Swager 2
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe detection of molecular isomers is a challenging and critical task for biotechnology and pharmaceutical industry. As a proof of concept, we report a chemiresistive material based on functionalized polythiophene and carbon nanotube hybrid system that can detect xylene isomers with high selectivity and sensitivity. We will describe in detail of polymer synthesis, device fabrication, sensing process, and the verification of the selectivity with a quartz crystal microbalance. We will also discuss our investigation of the sensing mechanisms, including charge transfer and conformational changes. This approach offers new low cost, real-time, low power sensors utilizing host-guest chemistry.
5:15 PM - BB4.8
X-ray Reactive Hyaluronic Acid Hydrogels.
Soeun Chang 1 , Byung Mook Weon 1 , Junseok Yeom 2 , Seikwang Hahn 2 , Taiho Park 3 , Jung Ho Je 1 , Yeukuang Hwu 4 , Giorgio Margaritondo 5
1 X-ray Imaging Center, Department of Materials Science and Engineering, POSTECH, Pohang, Gyungbuk, Korea (the Republic of), 2 Biomedical Nanomaterials Laboratory, Department of Materials Science and Engineering, POSTECH, Pohang, Gyungbuk, Korea (the Republic of), 3 Polymer Chemistry and Electronics Laboratory, Department of Chemical Engineering, POSTECH, Pohang, Gyungbuk, Korea (the Republic of), 4 Institute of Physics, Academia Sinica, Taipei Taiwan, 5 School of Basic Sciences, Ecole Polytechnique Fadarale de Lausanne, Lausanne Switzerland
Show AbstractPhase transition triggered by external perturbation is quite important in diverse fields ranging from physics to chemistry, biomedicine, and materials science. Fast transition is often required for a precise manipulation of hydrogels those are smart materials respond to a variety of external stimuli such as enzyme, ion concentration, electric field, pH, temperature, and light irradiation. In particular hyaluronic acid (HA) hydrogels that are natural polysaccharides have been widely studied as soft materials because of good biocompatibility and biodegradation. Rapid transition dynamics of HA hydrogels is required for advanced applications of tissue engineering, microdevices, and drug delivery with fast switchable response. However, HA hydrogels still exhibit a long response time for most stimuli. For instance, enzyme-triggered transitions need about a day for a full degradation of HA hydrogels. To diminish the transition time of HA hydrogels, we introduce a high intensive irradiation of X-rays to trigger phase transition in HA hydrogels. We present the first evidence of X-ray-reactive fast transition in HA hydrogels. We show that the fast transition (within a minute) is triggered by a brief irradiation of hard X-rays (10-60 keV). The fast transition is attributed to a rapid chain scission of HA hydrogels by X-ray irradiation. Real-time synchrotron X-ray imaging offers the direct evidence of the fast transition. The fast chain scission is characterized by comparing GPC (Gel Permeation Chromatography), UV, and FT-IR spectra of the irradiated and the reference samples. The GPC data show that the chain scission by X-ray irradiation significantly lowers the molecular weight for a short time. The FT-IR and UV spectra demonstrate that carbonyl or carboxyl groups are generated perhaps owing to the fast chain scission. We suggest that X-ray irradiation may offer the important advantage of the fast response time for HA hydrogels, opening up new and interesting technological opportunities.
5:30 PM - BB4.9
Two-way Shape Memory Polymer Composite and Its Application.
Woong-Ryeol Yu 1 , Seok Jin Hong 1 , Ji Ho Youk 2
1 Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Advanced Fiber Engineering, Inha University, Inha Korea (the Republic of)
Show AbstractShape memory polymers (SMPs) have attracted much attention from material scientists and engineers due to their potential applications to smart device and system such as sensors, actuators, medical implants, etc. Shape memory polymers (SMPs) have many advantages, such as easy processing to complex parts, low manufacturing cost, low density, and high shape recovery strain. Furthermore, SMPs show high levels of recovery strains larger than 100%, whereas shape memory metals or ceramics can recover several percentage points of deformation at most.The features of SMPs can be summarized in terms of their mechanical behavior. At temperatures higher than the transition temperature, they are deformed mechanically into a temporary shape. The temporary shape can be fixed by lowering the temperature and releasing the stress. At this time, the polymer molecules in SMPs tend to return to the permanent shape without deformation. However, since the rigidity in the molecules was increased by lowering the temperature, they could not take up all the deformation, thereby leaving the temporary shape fixed. Upon heating, the rigidity of the polymer chains in the soft-segment decreased and the frozen stress became activated such that SMP recovered all the deformation and returns to its permanent shape. Since on subsequent second heating, however, SMPs cannot deform into the temporary shape unless the mechanical stress is applied again, their behaviour is characterized as one-way shape memory behaviour. Some researchers have tried to develop two-way SMPs, i.e., upon the second heating they can deform into the fixed (or temporary) shape without the mechanical stress involved, however, versatile two-way SMPs has been not realized. Therefore in this study we have endeavored to develop two-way SMP composites using one-way SMPs and relying on their mechanical behavior. A possibility of manufacturing two-way shape memory polymer sensors will be presented at the Conference with an example composite that can change its length reversibly according to temperatures without explicit mechanical loading involved.
5:45 PM - BB4.10
First-Principles Calculations and Atomistic Simulations for Interaction of Gas Molecules with Polymer Separation Membranes in Crystalline Phase.
Yanting Wang 1 , Sergey Rashkeev 1 , John Klaehn 2 , Christopher Orme 2 , Eric Peterson 2
1 Center for Advanced Modeling and Simulation, Idaho National Laboratory, Idaho Falls, Idaho, United States, 2 Interfacial Chemistry, Idaho National Laboratory, Idaho Falls, Idaho, United States
Show AbstractGas separation membranes are widely used in many industrial, military, and scientific applications. The AMBER force field was applied to crystalline phases of three glassy polymers that are used as membranes for gas separation: Polybenzimidazole (PBI); Bis(isobutylcarboxy)polybenzimidazole (PBI-Butyl); and Kapton. Glassy polymer membranes are known to form amorphous and crystalline regions. Their crystalline structures were determined using classical molecular dynamics (MD) simulation techniques. The interactions of carbon dioxide (CO2) and nitrogen (N2) gases with these three polymers were studied by first-principle calculations (investigating possible binding of gas molecules to the polymer matrix and calculating their migration barriers and transition states) and by classical MD simulations (studying the behavior and evolution of large ensembles of gas molecules within crystalline polymers). We show that the packing structure and the interlayer coupling of polymer crystals determine the permeability of gas molecules. Crystalline PBI forms a very strong and closely packed crystalline structure, so that the gas molecules do not diffuse in the crystal. The crystal structure of PBI-Butyl is rigid, but the butyl side chains make the interlayer distances larger. Thus, the gas molecules can freely diffuse between the layers. The Kapton crystal structure is also closely packed, but the interlayer coupling is weaker than in PBI. As a consequence, gas molecules can be accommodated between the layers which increases the interlayer distances. Still, the molecules are not very mobile. For these glassy polymers, the qualitative behavior for the diffusion of CO2 and N2 molecules is quite similar, even though there are changes in polymer structures due to the presence of these molecules.
BB5: Poster Session: New Materials and Devices
Session Chairs
Zhongyang Cheng
D. Wrobleski
Thursday AM, December 04, 2008
Exhibition Hall D (Hynes)
9:00 PM - BB5.1
Amplified Fluorescence Turn-on Assay for Mercury(II) Based on Conjugated Polyfluorene Derivatives and Nanospheres.
Yusong Wang 1 , Bin Liu 1
1 Chemical and Biomolecular Engineering, National University of Singapore, Singapore Singapore
Show Abstract9:00 PM - BB5.10
Synthesis of Poly(Methylmethacrylate) Latex with Enhanced Rigidity through Surfactant Control.
Alex Wu 1 , K. Cho 2 , Irving Liaw 2 , Hua Zhang 2 , Robert Lamb 2 3
1 School of Chemistry, University of New South Wales, Sydney, New South Wales, Australia, 2 School of Chemistry, University of Melbourne, Melbourne, Victoria, Australia, 3 , Australian Synchrotron Company Ltd, Clayton, Victoria, Australia
Show Abstract9:00 PM - BB5.11
Portable Gas Sensor using Polydiacetylene (PDA) Supramolecule Embedded in Poly(ethylene glycol)diacrylate (PEG-DA) Hydrogel.
Sun Hee Park 1 , Gil Sun Lee 1 , Dong June Ahn 1
1 , Korea University, Seoul Korea (the Republic of)
Show Abstract There is great interest in the development of the efficient gas-sensors. For the gas-sensing, a variety of detection methods are used such as colorimetric, fluorescence and electrical detection method, etc. Among them, colorimetric methods have advantage that is possible on-site detection with naked eyes. Polydiacetylenes (PDAs) have two unique properties. One is color transition from blue to red upon various external stimuli such as temperature, pH, solvent, and ligand-receptor interaction. This color transition is caused by the reduction of the effective conjugated length of the backbone of PDAs. The other is self-emitting fluorescence characteristic. So the additional labeling procedures are not needed unlike conventional sensors. These unique properties of PDAs make these materials suitable as sensors. Although polydiacetylenes have been developed as the diverse sensor using these intriguing characteristic, the limitation for the portable sensor exists because they usually are used as the form of solution, LB film, and SAMs. Therefore we have developed a new strategy for a gel-based portable gas-sensor. To make a gel-based portable gas-sensor, PDAs have been embedded in poly(ethylene glycol) diacrylate (PEG-DA) hydrogel. This PDA-embedded hydrogel integrated hydrogel`s stability and PDA`s unique characteristics. So we have been realized the efficient and portable gas-sensor based on PDA-embedded hydrogel. After fabricating hydrogel to a form of strip, PDA-embedded PEG-DA strips were exposed to the various chemical vapors. The strips are attached to the cover of Pyrex Petri dish. And then a little amount of volatile chemicals placed on the bottom of dish. As the chemical evaporated, polydiacetylene was induced color transition and emitted fluorescence to specific gases. For a reuse of sensor, the reversibility of these transitions has been tested. We have reported that PCDA-mBzA (10,12-pentacosadiyonic acid-meta benzoic acid) shows optical reversibility in the condition of both vesicles and films (Ahn & Kim, J. Am. Chem. Soc., 2003, 125, 8976). PEG-DA strips embedding PDAs which composed of PCDA (10, 12-pentacosadiyonic acid) or PCDA-ABA (10,12-pentacosadiyonic acid-aminobutyric acid) have shown the irreversible response. On the other hand, PEG-DA strips embedding PDAs which composed of PCDA-mBzA (10,12-pentacosadiyonic acid-meta benzoic acid) have shown the reversible response. The results showed strip fabricated from PCDA-mBzA can be used as a reusable sensor. These PDA-embedded PEG-DA hydrogel will be extended to the various gases sensors by changing the moiety of headgroup of diacetylene monomers.
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New Immobilization Method Using DNA Hybridization and Its Application for Cyclodextrin Sensor.
Nari Kim 1 , Gil Sun Lee 1 2 , Dong June Ahn 1 2
1 Chemical and Biological engineering, Korea university, Seoul Korea (the Republic of), 2 Center for Integrated Nano Systems, Korea university, Seoul Korea (the Republic of)
Show Abstract Polydiacetylene (PDA) supramolecules have been widely investigated as a sensor due to unique colorimetric and fluorescent changes by external stimuli such as thermal transition, mechanical stress and ligand–acceptor interactions, that is, from blue to red and from non–fluorescent to red–fluorescent. Previously, many researchers have focused on developing PDA–based sensor in the form of aqueous liposome solution. Recently, we were successful in the development of PDA vesicle sensor immobilized on glass substrate. In this case, PDA vesicles were immobilized by covalent bonding between vesicle and glass substrate. These sensor systems are more sensitive against smaller amount of target molecule than solution–based sensors. In this study, we report that a new method for immobilization of PDA vesicles on the glass substrate using specific DNA hybridization. Immobilization of the vesicles on glass substrates was carried out by three steps. Firstly, amine–modified single–stranded DNA was printed on the surface of glass substrate with a conventional microarrayer. Secondly, amine–modified complementary DNA was reacted with PDA vesicles. Finally, hybridization was performed in the buffer containing complementary DNA bound with PDA vesicles. We demonstrate the interaction between cyclodextrins (CDs) and PDA vesicles in new immobilization method. After PDA vesicles reacted with α–CD, vesicles emitted red–colored fluorescence by itself due to a conformational change of the conjugated backbone of PDA by formation of the inclusion complex. However, PDA vesicles reacted with γ–CD did not emit red–colored fluorescence. Therefore, the immobilized PDA vesicles on surface could preferentially detect with α–CD over γ–CD. These patterned arrays could be also applied to rapid detection of multiple target molecules. These results are a first step towards developing sensor for detection of variable biomolecules such as DNA, protein, and cell.
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Effective Gas Sensing using Quartz Crystal Microbalance Modified with Polymer Nanobrushes.
Mutsumi Kimura 1 , Takashi Mihara 2 , Tadashi Fukawa 1
1 , Shinshu University, Ueda Japan, 2 , Olympus, Tokyo Japan
Show AbstractWe demonstrated weight-detectable quartz crystal microbalances (QCM) modified by various kinds of polymer brushes and investigated their sensing abilities for various organic gas molecules. These polymer brushes were attached onto the gold surface of QCMs through the combination of self-assembling monolayer formation and atom transfer radical polymerization (ATRP). ATRP polymerizations of three vinyl monomers from the initiator-modified QCMs resulted in the highly-dense polymer brush layer with 40-60 nm thickness. The responses on polymer brush coated QCMs exhibited reversible frequency changes for various gas species and the frequency changes depends on the chemical structures of polymer brushes as well as gas species. We believe that coating with polymer brushes will provide a new approach for the highly effective and selective molecular sensing nanolayers for atmospheric gas molecules.
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Core-shell Nanorods Prepared by Polymer Bilayer via Sequential Wetting.
Jinseok Byun 1 , Jin Kon Kim 1 , Dong Hyun Lee 2
1 Chemical Engineering, POSTECH, Pohang, Kyungbuk, Korea (the Republic of), 2 Polymer Science and Engineering, University of Massachusetts Amherst , Amherst, Massachusetts, United States
Show AbstractCore-shell structure consisting of two or more materials exhibits enhanced physical (or mechanical) and electrical properties that cannot be achieved by single component. In this study, we fabricated hexagonally packed core-shell nanorods consisting of poly (methyl methacrylate) (PMMA) as a core and polystyrene (PS) as a shell by sequential wetting of PS/PMMA bilayer film inside anodized aluminum oxide (AAO) template. We found that the reactive bilayer consisting of PMMA with epoxy functional group (PMMA-GMA) and PS with end terminated carboxylic acid functional group (PS-mCOOH) is necessary to form the well-defined core-shell nanorods. By the in-situ formed graft copolymers from the reaction, the lower PMMA layer was able to spread onto pre-formed PS wall as a sequential wetting. The sizes of the core and the shell are easily controlled by adjusting the thickness of each layer. On the contrary, a non-reactive bilayer without having reactive functional groups could not generate the core-shell structure, but simple single nanorod due to non-spontaneous spreading (negative spreading coefficient).
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Fabrication of Hierarchical Structures on Polymer Surfaces and Their Novel Wetting Properties.
Yuwon Lee 1 , Kuk-Youn Ju 1 , Jin-Kyu Lee 1
1 Chemistry, Seoul National University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - BB5.17
Nanopatterning by using Block Copolymer Baroplasticity.
Ara Jo 1 , Jin Kon Kim 1 , Wonchul Joo 1
1 Chemical Engineering , Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractWe prepared high-density nanopatterns by using atomic force microscope (AFM) at room temperature. For this purpose, we employed polystyrene-block-poly(n-pentyl methacrylate) copolymer (PS-b-PnPMA) having baroplasticity. PS-b-PnPMA thin film with an ordered state becomes high mobility upon pressure through the transition to disordered state. This unique property does not require any heating which is necessary for the existing technology such as IBM millipede method. We can convert the depth to electric signal (0 and 1) by using piezoelectric sensing method.Acknowledgement: This work was supported by Creative Research Initiative Program supported by KOSEF
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Miscible Blends of Linear and Crosslinked Poly(ε-caprolactone) for Shape Memory Assisted Self-Healing.
Erika Rodriguez 1 , Xiaofan Luo 1 , Patrick Mather 1
1 Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York, United States
Show AbstractWe report on miscible blends of linear and crosslinked poly(ε-caprolactone) (L-PCL/n-PCL) exhibiting a combination of shape memory response and self-healing capacity. The crosslinked component, n-PCL with a network chain molecular weight (Mc) of 3,000 g/mol, affords reversible plasticity – a form of shape memory where apparently plastic deformation is fully recoverable upon heating above the blend melting temperature (Tm ~ 55 C). The linear component, L-PCL with a molecular weight of 65,000 g/mol, interpenetrates the shape memory n-PCL component, yet freely diffuses above Tm to yield a tacky surface capable of rebonding any cracks formed during damage. The L-PCL component incorporation was varied to include 0, 50, 60, and 70 percent, allowing quantification of the competition between network elasticity (n-PCL) and rebonding by L-PCL diffusion. Dynamic Mechanical Analysis (DMA) tests have revealed that all blends studied have the ability to be cold-drawn to 200 percent tensile strain at room temperature (T~25 C) and this strain remains well “fixed” with time. The apparently plastic deformation can be recovered completely to its original shape by heating to a temperature T > Tm. For samples containing sufficient L-PCL, this heating event is accompanied by surface tackification and, for the case of pre-cracked samples, rebonding at the crack-surfaces, revealing shape memory assisted self-healing. We observe near-complete recovery of mechanical properties for damaged samples healed in this manner. We anticipate utilization of these new materials in coatings, adhesives, and films where long-term use facile repair are needed.
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Novel Enzymatic Polymerization of Diazo Compounds. A New group of Dyes.
Ferdinando Bruno 1 , Diane Stevees 1 , Lauren Belton 1
1 Material Science, US Army Natick Lab, Natick, Massachusetts, United States
Show AbstractIn the past 20 years enzymatic polymerization has been used successfully for the formation of macromolecules. Their mild polymerization conditions, the environmental compatibility and their high selectivity are a clear advantage compared to the traditional procedure. Enzyme such as horseradish peroxidase is currently frequently implemented to polymerize intricate macromolecules that are prohibited with a classical chemical procedure. Horseradish peroxidase was utilized to catalyze the polymerization of phenol and aniline derivatives for the formation of conductive/conjugated polymers.Here we present the enzymatic polymerization of Sudan Orange G, Disperse Orange 3, Calcon, Mordant Yellow 12, Disperse Orange 13, and Bismark Brown Y mediated by horseradish peroxidase. The enzymatic reaction produces a novel electroluminescence polymer that exhibits a red or a blue shift compared to the solitary monomer. The product can be cast to produce optical quality films without noticeable mechanical instability.Furthermore we will present extensive characterization based on spectroscopy, and thermal analysis. Preliminary efforts to utilize these polymers in an LED will be discussed.
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Using Liquid Crystal as Bio/Chemical Responding Material in an Integrated Sensing Device.
Daming Cheng 1 , Hongrui Jiang 2 1
1 Materials Science Program, University of Wisconsin-Madison, Madison, Wisconsin, United States, 2 Electrical & Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show Abstract9:00 PM - BB5.21
pH Sensor Based on White Light Interferometry Using Polymeric Nano Coatings [upna].
Carlos Ruiz 1 , Javier Goicoechea 1 , Francisco Arregui 1 , Ignacio Matias 1
1 Electric and Electronic Engineering, Public University of Navarra, Pamplona, Navarra, Spain
Show AbstractWe introduce here a fiber optic pH sensor based on white light interferometry [1] which overcomes the main drawbacks of many optical fiber pH sensors such as their dependence to optical power variations or leaching of the indicators. The main strength of this work is that we can measure changes in pH by monitoring the changes in wavelength, using a polymeric colorless matrix and a low-coherence light source as a the excitation source, what means a very robust, simple and cost-effective method.Merging the modern deposition techniques with white light interferometry methods allow us to monitor ultrathin structures at nanometer scale over nearly any substrate. Here, the electrostatic Layer-by-Layer (LbL) technique [2] was used to create thin polymeric films onto standard optical fiber ends which operate as a Fabry-Perot Interferometric (FPI) etalon of a few hundreds of nanometers [3] suitable to be excited with a halogen white light source. The basic structure of these polymeric films consisted on the alternate deposition of the weak polyelectrolytes, poly(allylamine hydrochloride) (PAH) as the cationic material, and the polymer poly(acrylic acid) (PAA) as the anionic one. In this case, the colorless polymeric matrix swells and deswells, changing its morphology (thickness) depending on the pH of the surrounding medium [4]. Then, the colorless polymeric matrix acts as the interface between the optical fiber and the external medium, working as a variable length FPI which will change its spectral response according to the variations in pH.In this work, we use a simple optical reflection setup which consists mainly on a white light source that launchs light into a standard communications multimode 50:50 optical fiber splitter connected to the optical fiber sensor tip on one side and to a CCD spectrometer on the other side. Different structures are characterized depending on the parameters used in the fabrication process such as pH of fabrication, molecular concentration and immersion times. Then, several experiments were carried out with the sensors fabricated, showing variations in wavelength of the spectral response of the sensor depending on the pH of the medium. By using a peak detection algorithm that locates the maximum reflectance peaks along the spectrum we can obtain the pH by determining the wavelength of maximums reflectance peaks detected. The results obtained show a maximum variation in wavelength of 45 nm per pH unit in the best case, with an acceptable response time and sensitivity between 0.051 and 0.0187 pH units for the best and worst case respectively demonstrating the feasibility of using this amplitude independent technique to measure pH.[1] J. Goicoechea et al, IEEE Sensors (2007) 399-402[2] G. Decher et al,. Ber Bunsenges. Phys. Chem., 1991, 210/211, 831-835.[3] F. J. Arregui et al, Optics Letters, 24(9), (1999) 596-598[4] Rubner et al, Macromolecules, 38 (2005) 3450-3460
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Synthesis and Properties of Linear and End-Grafted Thermosensitive Random Copolymers with LCST Behavior.
Naomi Kumano 1 , Yukikazu Takeoka 1 , Takahiro Seki 1 , Taisuke Kawamoto 2 , Hisashi Haga 2 , Kazushige Kawabata 2
1 molecular design and engineering, Nagoya university, Nagoya, Aichi, Japan, 2 Division of Biological Sciences, Hokkaido university, Hokkaido, Sapporo, Japan
Show AbstractAdvanced researches for tissue engineering require smart and soft surfaces for various cell culture environments. Particularly, stimuli-switchable surfaces capable of performing reversible bio-interactions are highly relevant for regenerative medical techniques.Such smart and soft surfaces can be constructed with stimuli-responsive polymers.The thermo-responsive poly (N-isopropylacrylamide) (poly(NIPAM)) has been widely investigated for preparing bio-relevant switchable surfaces, because poly(NIPAM) exhibiting a lower critical solution temperature (LCST) at 32°C in water can be modified on various sold surfaces and the surfaces show hydrophilic-hydrophobic change between room and body temperature. However, one of the draw backs of poly(NIPAM) is that this not biocompatible.Moreover, new switchable surfaces modified with thermo-responsive polymers exhibiting different LCST are needed for the application to various systems.In this context, the development of efficient and tailor-made switchable surfaces based on polymers of biocompatible component is certainly becoming a topical matter.Recently, the predominance of poly(NIPAM) as the paradigmatic example of thermoresponsive polymer was challenged by the discovery that random copolymers of 2-(2-methoxyethoxy)ethyl methacrylate (MEO2) and oligo(ethylene glycol) methacrylate with an average of nine repeating units of ethylene glycol as a side chain (MEO9) exhibit a LCST in water. This polymer can be finely tuned anywhere between 26 and 90°C depending on the relative proportions of each monomer.The linear random copolymers of MEO2 and MEO9 monomers (poly(MEO2-co-MEO9)) with a tunable LCST were synthesized by atom transfer radical polymerization (ATRP), and the thermosensitive behaviors of the polymers in water was observed by turbidity measurement.The LCST of these linear copolymers could be easily tuned by adjusting the fraction of MEO9 units in the copolymer chains.Next, the thermoresponsive surfaces with a tunable wettability were prepared by growing brushes of poly(MEO2-co-MEO9) copolymers from cleaned silicon wafers modified with a silane ATRP initiator so-called the “grafting-from” method. The thermosensitive behavior of the polymer-grafted surfaces was observed in water at different temperatures by contact angle measurement.A dramatic change in the wettability of the homopolymer composed of MEO2 grafted on the silicon wafer was observed in a temperature range from 18°C to 28°C.The temperature range where the wettability changes was shifted to higher temperatures with increasing the MEO9 content in the random copolymers. Thus, the wettability on the surface can be tuned on demand by adjusting the initial composition of the comonomer feed.The interactim mode with water and morphologies of poly(MEO2-co-MEO9) film in water were further studied by means of IR spectroscopy and scanning probe microscope, respectively.
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Kinetics of Nucleic Acid-lipid Self-assembling Complexes for Drug Delivery on Biochips Using ATR Analysis.
Thorsten Neumann 1 2 , Surekha Gajria 2 1 , Wirasak Smitthipong 1 3 , Luc Jaeger 2 1 , Matthew Tirrell 3 1
1 Material Research Laboratory, University of Santa Barbara, Santa Barbara, California, United States, 2 Chemistry and Biochemistry, UC Santa Barbara, Santa Barbara, California, United States, 3 College of Engineering, UC Santa Barbara, Santa Barbara, California, United States
Show AbstractNegatively charged nucleic acids such as RNA and DNA can self-assemble with cationic lipids such as didodecyldimethylammonium bromide (DDAB) via electrostatic complexation to form water-insoluble complexes capable of forming self-standing films when cast from an organic solvent such as isopropanol, as previously reported. To further explore and manipulate the biocompatibility of our self-assembling nucleic acid-lipid films we need to determine the melting temperatures of the various complexes as well as any structural reorgannization that takes place during changes in their environmental temperature. In addition we also wish to better understand their rate of biodegradation and drug release. Due to the need for less material and high throughput analysis we printed small amount of different nucleic acid complexes labeled with various fluorescent dyes (such as Sybr Gold and ethidium bromide) on a PMMA biochip, which can be used to understand the kinetics of degradation for several samples in parallel. To analyze the biochips we built a biochip reader which is based on the ATR principle (attenuated total internal reflectance fluorescent reader) with a temperature controlled flow cell that is able to continuously analyze the fluorescence signals of all samples on the chip. We have used this technique to determine the biodegradation of the nucleic acid-DDAB complexes in blood serum and their melting temperatures in buffer using nucleic acid-intercalating fluorescent dyes. Daunorubicin, which is a fluorescent nucleic acid-intercalating cancer drug, was also used as a model for a drug delivery system. We have seen that by changing the type of nucleic acid used in the lipid complex we can vary the degradation rate and the rate of drug release.
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Nanoscale Ionic Materials, NIMS.
Robert Rodriguez 1 , Lynden Archer 2 , Emmanuel Giannelis 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States
Show Abstract9:00 PM - BB5.25
High-Performance and Hierarchically-Structured Composites Prepared with Layer-by-Layer Assembly Technique.
Paul Podsiadlo 1 , Amit Kaushik 2 , Kheng Eugene 2 , Bong Sup Shim 1 , Jungwoo Lee 3 , Hyoung-Sug Kim 5 , Si-Tae Noh 5 , Anthony Waas 6 , Ellen Arruda 2 , Nicholas Kotov 1 3 4
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 5 Chemical Engineering, Hanyan University, Ansan Korea (the Republic of), 6 Aerospace Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract9:00 PM - BB5.26
Photo-Responsive Liquid Crystalline Polymers.
Eric Verploegen 2 , Tejia Zhang 3 , Mariel Kozberg 1 , Johannes Soulages 4 , Paula Hammond 1 , Gareth McKinley 4 , Michael Petr 1
2 Materials Science Engineering, MIT, Cambridge, Massachusetts, United States, 3 Chemistry, MIT, Cambridge, Massachusetts, United States, 1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States, 4 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractWe have developed a class of photo-responsive liquid crystalline moieties andattached them to a low glass transition siloxane polymer backbone. Thesematerials undergo a conformational change upon exposure to ultra-violet light. This conformational change alters the self-assembled morphology and in turnsignificantly impacts the mechanical properties of the material. We are ableto reversibly alter the shear modulus of these materials by several orders ofmagnitude through exposure to ultra-violet light. This class of materialsshows great promise for use in many robotics applications.
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Fabrication and Transfer of Aligned Carbon Nanotube-Polymer Nanostructures.
Yu Mao 1 , Yumin Ye 1
1 Department of Biosystems Engineering , Oklahoma State University, Stillwater, Oklahoma, United States
Show Abstract9:00 PM - BB5.28
Multivesicle Assemblies Based on the Layer-by-Layer Deposition with Block Copolymer Micelles.
Jinkee Hong 1 , Kookheon Char 1 , Jinhan Cho 2
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 2 School of Advanced Materials Engineering, Kookmin University, Seoul Korea (the Republic of)
Show AbstractWe present the versatile well-controlled capsule structure with functions, which is based on the self-assembled block copolymer micelles. Charged block copolymer micelles (BCMs) containing hydrophilic and hydrophobic segments, such as polystyrene-b-poly(acrylic acid) (PS-b-PAA) and polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP), can incorporate hydrophobic functional materials (e.g., nanoparticles, dyes, and so forth) into the hydrophobic cores of the micelles in water. We previously reported that charged BCMs containing hydrophobic organic dyes can be deposited in the layer-by-layer (LbL) fashion with BCMs with complementary charge on both flat and colloidal substrates. Specifically, in the case of multilayer films assembled with cationic PS-b-P4VP and anionic PS-b-PAA, because of aggregation between adsorbed micelles, the size of porous domains is strongly dependent on the charge density of hydrophilic corona chains, molecular weight, and the number of bilayers of BCMs. Based on the stable growth of BCM multilayers, we investigated the morphology of film surface deposited with both hairy and crew-cut BCMs. Our approach highlights the potential to incorporate a range of active ingredients for biomedical applications into the assembled BCMs to yield multifunctional polymeric multivesicle assemblies.
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Tuning Lower Critical Solution Temperature of Stimuli-responsive Smart Polymers.
Qiang Yuan 1 , Devesh Misra 1
1 Center for Structural and Functional Materials, University of Louisiana at Lafayette, Lafayette, Louisiana, United States
Show Abstract9:00 PM - BB5.31
A Route Toward Wet Spinning of Single Wall Carbon Nanotubes (SWCNTs) Fibers: Sodium Alginate – SWCNT Fibers.
Vijoya Sa 1 , Konstantin Kornev 1
1 Material Science and Engineering, Clemson University, Clemson, South Carolina, United States
Show AbstractSingle walled carbon nanotubes (SWCNT) are attractive object of nanotechnology because of their unique tensile properties (high modulus and tensile strength) and electrical conductivity. Conventional methods of dispersion of SWCNTs in polymer films and fibers provide very low loading of SWCNTs, typically in the range of 0.1 - 2 wt % [1]. Making fibers with high SWCNTs loading is a challenge posed by physico-chemical nature of carbon nanotubes. On the other hand, high loading of SWCNTs is required for making artificial muscles, supports for biomedical sensors, supercapacitors, microwires, etc. The most popular approach [2, 3] to spin fibers from SWCNT solution assumes injection of the SWCNTs dispersion into a dilute solution of polyvinyl alcohol (PVA). PVA coagulates upon contact with a jet of SWCNTs dispersion and forms ribbons and fiber-like precursors, which have to be gently withdrawn from the coagulation bath and post treated to obtain a fiber. In this process, the concentration of SWCNTs in the fibers is very difficult to control, and, typically, the polymer/SWCNTs composition is unknown. While this process and fibers are important for understanding the mechanisms of fiber formation from carbon nanotubes, the method is almost impossible to implement in industrial setting. As an alternative to this approach, we propose a new method based on conventional wet spinning technique. The idea is to exploit electrostatic assembling of SWCNTs coated with Sodium Dodecyl Sulphate (SDS). Many polymers important for applications, for example, alginate, chitosan, and polyacrilamide crosslink by ionic crosslinkers. Hence, if one manages to introduce SWCNTs-SDS into the network of these polymers, the resulting material is expected to be very strong and functional. We report on successful spinning of alginate fibers with carbon nanotube loading as high as 23 wt %. The Young’s modulus increases up to 20 GPa at 23 wt % loading of SWCNTs in the Alginate-SWCNT fibers. A transition from a composite structure (SWCNTs sitting in alginate matrix) to a two-component polymer structure (SWCNTs + Alginate) is discussed using the results of rheological, mechanical, morphological, and electric conductivity characterizations. References: 1)Bhattacharyya et. al, Polymer, 44 (8), 2373 - 2377 (2003).2)Vigolo et. al, SCIENCE VOL 290 17 NOVEMBER 2000, pp 1331-1334.3)Kornev et. al, Physical Review Letters 97, 188303 (2006).
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Novel Green Technique for Enhancing Low Dielectric Properties of Polymer Thin Films using Supercritical Carbon Dioxide.
Peter Gin 1 , Tadanori Koga 1 , Toh-Ming Lu 2 , Cynthia Gedelian 2
1 Materials Science and Engineering, Stony Brook University, Stony Brook , New York, United States, 2 Physics, Applied Physics, and Astronomy, and Center for Integrated Electronics, Rensselaer Polytechnic Institute , Troy, New York, United States
Show AbstractWith the continuous drive and demand for higher performance integrated circuits, coupled with increased portability requirements, novel approaches towards the development of new low-dielectric constant (low-k) materials for future microelectronic applications must be investigated. We have established a novel “green” methodology that produces high-quality homogenous low-density amorphous polymer thin films using supercritical carbon dioxide (scCO2)[1]. In this presentation, we report creatingthe unified process combined scCO2 and an organic solvent (such as toluene), which was used before scCO2 exposure to melt the crystal structures of PPV films and to facilitate the effect of scCO2, and the creation of homogenous low-density PPV films (up to 50 nm in thick) with a reduction of 20% in density. Further, we found that the dielectric constant of the low-density PPV film decreased by 25% relative to the untreated PPV film, indicating that the exposed PPV film has the k value of about 2.0.[1] Koga et al., Appl. Phys. Lett. 83 (2003) 4309.
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Hydrogen Generating Gel Systems Induced by Visible Light.
Kosuke Okeyoshi 1 , Ryo Yoshida 1
1 Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo Japan
Show Abstract9:00 PM - BB5.34
Electron Tomography Study of the Ordering Process of Double-Gyroid Network Structures in Block Copolymer/Homopolymer Blends.
Hirokazu Hasegawa 1 , Satoshi Akasaka 1 , Tetsuro Okamoto 1 , Vincent Mareau 1 , Taketsugu Osaka 1 , Tadashi Matsushita 1
1 Department of Polymer Chemistry, Kyoto University, Kyoto, Kyoto, Japan
Show AbstractBlock copolymers self-assemble to form highly regular phase-separated structures in nanometer scale and their 2D and 3D patterns are useful for a variety of functional materials for nanotechnology such as nanolithography, photonic crystals, nanoporous membrane, etc. One of the current issues in this field is how to prepare a defect-free array of microdomains. Among many different microdomain morphologies, double-gyroid network structure (DG) with Ia3d symmetry is of interest because of the 3D bicontinuity of the constituent polymers. One of the effective ways to control the microdomain structure is to utilize the phase transition such as disorder-order or order-order transition. The ordering process, e.g., during solution casting or annealing may be controlled to reduce the defects and to increase the grain size.We investigated the ordering process during slow-casting of toluene solution of the blends of polystyrene-block-polyisoprene diblock copolymer (PS-b-PI) and polystyrene homopolymer (hPS). Neat PS-b-PI (49k-30k) has a slightly asymmetric composition but forms lamellar microdomains. The microdomain morphology of the blends changes with blend composition since hPS (44k) is in the wet-brush regime. In a narrow range of the blend composition, which we call the “complex phase window”, DG and perforated layers (PL) as well as irregular networks (sponge) appear in the cast films. DG seems to be a stable structure in this composition range and DG grains grow by consuming PL and sponge structures. Therefore, by observing the grain boundaries between DG and PL or DG and sponge, we can conjecture the mechanisms of morphological transitions. We employed electron tomography, which is an excellent technique to observe the grain boundaries and lattice defects especially for such a complex structure as DG. We successfully revealed how the DG grains self-organize to grow and how the defects are healed during the casting process.
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Preparation and Carbonization of Macroporous Poly(divinylbenzene) Gels via Living Radical Polymerization.
Joji Hasegawa 1 , Kazuyoshi Kanamori 1 , Kazuki Nakanishi 1 , Teiichi Hanada 1 , Shigeru Yamago 2
1 Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto Japan, 2 Institute for Chemical Research, Kyoto University, Kyoto Japan
Show AbstractPorous polymer monoliths with well-defined morphology and controlled pore size are useful in many applications, for example, separation, adsorption, ion exchange and so on, owing to their high surface area, easy chemical modification etc. Moreover, porous carbon materials, which can be obtained by heat treatment of porous polymer monoliths, are used for many industrial applications such as adsorbents, filters, thermal insulators, heat exchangers and fuel cell electrodes. Such polymer monoliths are conventionally prepared with a free radical polymerization technique, but fine control of morphology, pore size and volume is rather difficult due to the heterogeneous network formation by free radical polymerization. To better control the pore properties, spinodal decomposition in the homogeneous network that can be available with living radical polymerization has been considered in this study.We utilized organotellurium-mediated living radical polymerization (TERP) that can provide well-defined polymers from a variety of vinyl monomers via degenerative chain-transfer polymerizations. These polymerizations with high controllability can be attributed to the rapid degenerative-transfer process between the polymer-end radicals and corresponding dormant species. By TERP, macroporous crosslinked polymer gels have been obtained in solvent with existence of counter polymer, poly(dimethylsiloxane) (PDMS). Incorporating PDMS induced macroscopic spinodal-type phase separation during the course of polymerization of divinylbenzene (DVB), and the transient phase-separating structure was frozen by gelation. Well-defined macroporous morphology consisting of continuous poly(divinylbenzene) (PDVB) skeletons has thus been obtained after removing the solvent and PDMS. By altering the concentrations of PDMS and the solvent, macropore size and volume were independently controlled. They also have micro- and mesopores which may be derived from the interstices between the PDVB networks, and from the micro-phase separation between PDMS and PDVB inside the skeletons, respectively. Macroporous PDVB gels prepared as described above were sulfonated in concentrated surfuric acid and heat-treated under nitrogen atmosphere to be carbonized. Sulfonation reduced the shrinkage and weight loss of the gels during carbonization. Therefore it was possible to retain not only macropores but also meso- and micropores even after carbonization. The resulting carbon gels with preserved macroporous structure had high surface area attributed to micropores when they were treated at more than 1000 deg C. Furthermore, when the carbon monoliths were activated, i.e. heat-treated under nitrogen/carbon dioxide atmosphere, the surface area reached as high as general activated carbons as a result of generating a lot of micropores. Using this method, we can obtain new carbon materials simultaneously possessing three different sizes of pores; macro-, meso- and micropores.
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Template Synthesis of Stimuli-responsive Angle Independent Structural Colored Gel.
Mohammad Rashid 1 , Abu Imran 1 , Takahiro Seki 1 , Yukikazu Takeoka 1 , Masahiko Ishii 2 , Hiroshi Nakamura 2
1 Molecular Design and Engineering, Nagoya University, Nagoya, Aichi, Japan, 2 , Toyota Central R&D Labs., Inc., Nagakute, Aichi, Japan
Show AbstractTemplate synthesis is a well-known route to fabricate smart materials. Chemical gels can memorize the properties of periodic ordered templates and thereby display dynamic and optical abilities, imposed by the properties of the templates. Structural colored gel made of a closest packed colloidal crystal as a template exhibits specific color based on Bragg diffraction of light and the color depends on the angle of view and the angle of illumination. To devise wide-angle color display, special template with angle independent structural color is required. In this work we present a new material which is a 3D solid random system like photonic glass and can be used for a template to fabricate an angle independent structural colored gel. This new 3D system is composed of silica spheres (300 nm) arranged in a completely random state. The adopted method takes advantages from the two body interaction between the silica spheres in a colloidal suspension. First a 20 ml NaCl solution of 0.5 M was added to a 20 ml of 21 wt.% aqueous suspension of silica colloidal spheres. The final suspension was centrifuged to force the coagulation of the spheres. As a result, a viscous slurry was obtained. To prepare the template with controllable thickness and uniformity, a sandwich like frame was contrived by clipping two pre-cleaned glass slides separated with 1 mm thick teflon spacer. A volume of viscous slurry was poured into the gap of the sandwich and dried at 60 °C for 6 h. A faint colored solid comprised of roughly-packed colloidal particles was prepared from the same type of colloidal suspension as used for making a closest packed colloidal crystal. Several investigations were carried out to check the angle independent optical behaviors of the prepared material. Scanning electron microscopy (SEM) image evidences that the newly fabricated material consists of roughly-packing of the silica spheres like a photonic glass. The presence of ions in the colloidal suspension influences the interaction between spheres and mutates the initial repulsion into attraction. The addition of salt breaks the stability of suspension and enhances coagulation which leads to random orientation of the particles. The reflection and transmittance spectra of the random ordered system were measured by changing incident angle in different solvents. Unlike colloidal crystal broad ditches were observed in transmittance spectra. When the incident angle was altered, the peak position of the colloidal crystal shifted but that of random ordered system remained unchanged. A faint angle independent structural color can be observed from the developed material. To establish an independent measure of the ordering of our system, autocorrelation and 2D Fourier analysis of SEM image are going to be executed. This photonic material can be used as a template to make an angle independent structural colored gel as well as a medium to investigate light propagation, random laser and Andersion localization.
9:00 PM - BB5.38
Fabrication of Model Colloidal Systems with Tunable Optical Properties for Self-Assembly Study.
Adeline Perro 1 , Guangnan Meng 1 , Ryan McGorty 1 , Vinothan Manoharan 1
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractWe have synthesized new types of micrometric particles composed of small fluorescent polystyrene cores and large crosslinked poly(N-isopropylacrylamide) polyNIPAM shells. The optical properties of polyNIPAM shells were modulated optimizing several experimental parameters such as the crosslinking degree. Immersed in water at ambient temperature, the shell of these particles is swollen, inducing that optical properties (absorbed, scattered light) were controlled only by the small polystyrene core limiting interference effects between scattered waves from different particles. Raising the temperature to transition temperature leads to a decrease of the thermosensitive shell volume inducing strong variations in the optical properties of the core-shell colloids.We present some preliminary studies on the self-assembly of these core-shell colloids characterized by confocal microscopy and digital holographic microscopy. The resulting phase diagram of these core-shell colloids will be compared to the phase behavior of hard spheres.
9:00 PM - BB5.39
Global Molecular and Microstructural Orientation of Spin Coated Thin Ferroelectric Poly(vinylidene Fluoride-co-trifluoroethylene) Films by Static Shearing.
Jiyoun Chang 1 , Hee June Jeong 1 , Youn Jung Park 1 , Seok Ju Kang 1 , Cheolmin Park 1 , Bernard Lotz 2 , June Huh 3
1 Materials Science and Engineering, Yonsei University , Seoul Korea (the Republic of), 2 , Institut Charles Sadron(CNRS-ULP), Strasbourg France, 3 Materials Science and Engineerin, Seoul National University, Seoul Korea (the Republic of)
Show AbstractThe polymer ferroelectrics mostly represented by semi-crystalline poly vinylidene fluoride(PVDF) and its copolymers with trifluoroethylene(TrFE) have been of great attention for the potential application of nonvolatile ferroelectric polymer memory. A thin P(VDF-TrFE) film obtained from spin-coating and subsequent thermal annealing is usually composed of semi-crystalline lamellae randomly oriented on azimuthal plane which in turn ruin the consequent ferroelectric properties of the film due to the reduced net polarization of the polymer across top and bottom electrodes. For high performance polymer memory, the control of molecular and microstructural orientation is, therefore, the one of the most important factors. Here we present a new route for fabricating a thin PVDF-TrFE film with very large area molecular and microstructural ordering. The method is simply based on the static mechanical shearing of the film under appropriate thermal conditions. The apparatus designed in particular for ultra thin PVDF-TrFE films with the thickness of 200 nm or less allowed us to fabricate a thin film in which ca. 20 nm thick crystalline lamellae were globally ordered perpendicular to the shear direction. Grazing Incident X-ray Scattering further revealed the molecular ordering of the film with a and c axis of the PVDF-TrFE crystals preferentially oriented parallel to the film normal and the shear direction, respectively. Both metal/PVDF-TrFE/metal capacitor and ferroelectric field effect transistor with the sheared PVDF-TrFE dielectric layer exhibited the enhanced ferroelectric properties arising from the globally ordered molecular microstructure.
9:00 PM - BB5.4
Tunable Quantum Confinement Effect on Non-volatile Thin Film Polymer Memory Device.
Augustin Hong 1 , Kang Wang 1 , Dayanara Parra 2 , Sarah Tolbert 2 , Wei Lek Kwan 3 , Yang Yang 3
1 Electrical Engineering, University of California at Los Angeles, Los Angeles, California, United States, 2 Chemistry, University of California at Los Angeles, Los Angeles, California, United States, 3 Materials Science and Engineering, University of California at Los Angeles, Los Angeles, California, United States
Show Abstract9:00 PM - BB5.40
Temperature Responsive Wetting between Hydrophilicity and Superhydrophobicity on Micropillar Arrays Grafted with Mixed Polymer Brushes.
Yue Cui 1 , Shu Yang 1
1 Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show Abstract9:00 PM - BB5.41
Materials Properties of Polymer Blends of Poly(3,4-ethlenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) and Polyvinyl Alcohol (PVA).
Chang-hsiu Chen 1 , Richard Nelson 2 , John LaRue 3
1 Chemcial Engineering & Materials Science, University of California, Irvine, Irvine, California, United States, 2 Electrical Engineering & Computer Science, University of California, Irvine, Irvine, California, United States, 3 Mechanical & Aerospace Engineering, University of California, Irvine, Irvine, California, United States
Show AbstractThe structure material of microelectromechanical systems (MEMS) has been built with two polymer blends. It has tremendous applications in BioMEMS areas and optical electronic fields. Poly(3,4-ethlenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) is a high conductivity polymer. And a water soluable non-conductive synthetic polymer, polyvinyl Alcohol (PVA), leads to increase tensile strength, durability and flexibility. Mixtures were prepared and spin coated to form thin films. Detailed process of fabrication technique will be presented. The AC and DC electrical properties of the thin films are studied using the four point probe method. Studies of electrical properties will lead materials to different applciations. And the mechanical properties, such as Young’s Modulus and tensile strength of the thin films were measured by resonance frequency and capacitance measurement. Young's Modulus of polymer blends are about 1-5GPa. These lower Young's Modulus polymers than metals can minimize the dimension of MEMS devices and other applications. The film conductivities increased proportional to the increase in conducting polymer PEDOT:PSS content. And thin films became ductile from brittle with increasing PVA content. In addition, (N-Methyl-2-pyrrolidinone), a conductivity enhancer, was introduced and resulted in an increase of the conductivity of the polymer blends with the order of 100.
9:00 PM - BB5.42
Preparation of Conducting Polymer Actuators using Ionic Liquid and Cation Drive Properties.
Kentaro Yamato 1 , Kazuo Tominaga 1 , Wataru Takashima 2 , Keiichi Kaneto 1
1 Graduate School of Life Science and Systems Engineering, Kyushu Institute of technology, Kitakyushu Japan, 2 Research Center for Advanced Eco-fitting Technology, Kyushu Institute of technology, Kitakyushu Japan
Show Abstract9:00 PM - BB5.5
Gold Nanoparticles on Nanopatterned Surface of BlockCopolymer.
SaeHyun Park 1 , Jonghwi Lee 1
1 Chemical Engineering, Chungang university, Seoul, Dong jak gu, Korea (the Republic of)
Show AbstractINTRODUCTIONThe use of block copolymer thin films as self nanopatterned polymeric substrates has become popular as an economical nanofabrication technique, with new applications and techniques constantly being developed. There is a growing interest in the use of gold nanoparticles modified with biomolecules for the rational design of nanostructured functional materials and their use in electronic, optical, and biosensor applications. This study investigated the interactions between gold nanoparticles protected by polymeric electrolytes and the nanopatterened surfaces of poly (styrene-b-ethylene oxide) (PS-b-PEO). MATERIALS AND METHODSThin films of PS-b-PEO were deposited on an Indium Tin Oxide glass by spin coating and subsequent solvent annealing. Gold nanoparticles are chemically prepared through the reduction of tetrachlorauric acid. The nanoparticles are polymer protected and water dispersible. The patterned polymeric substrate (nanotemplate) was dipped into a gold colloidal solution. Through this process, the ordered gold nanoparticles monolayer was obtained. It was analyzed using Atomic Force Microscopy (XE-100, PSIA). RESULTSAFM characterization of nanopatterned surfacesPatterned polymeric substrates have the ordered cylindrical domains of 20-30 nm. This thin film consists of hydrophilic PEO cylindrical domain and hydrophobic PS surfaces. The surface of the substrate was confirmed by using AFM. Ordered nanoparticles arraysThe surface topography of the nanostructured 2D array of gold nanoparticles was analyzed using AFM. It was clearly confirmed that gold nanoparticles covered the nanopore arrays of the substrate. They followed the regularity of the substrate patterns.Gold nanoparticles characterizationA series of gold nanoparticles with various diameters were in situ synthesized by reduction of tetrachloroauric acid trihydrate with a reducing agent in the presence of polymers with different physical properties. Gold nanoparticles were analyzed by using Transmission Electron Microscopy , X-ray Diffraction and Infrared spectroscopy.CONCLUSIONSThe 2D array of gold nanoparticles was prepared on the nanopatterned polymeric substrate having hydrophilic and hydrophobic domains. The surface where the water dispersible gold nanoparticles existed was the hydrophilic PEO domain. Our present studies demonstrate that the regularly ordered monolayer of gold nanoparticles can be achieved on a polymeric film by a solvent annealing method, and nanoparticles of relatively diverse properties and size distributions can be used. The surface of nanopatterned arrays before and after the step of monolayer formation was examined by using the Atomic Force Microscopy (XE-100, PSIA).
9:00 PM - BB5.6
Polymer-stabilized Chiral Nematic Liquid Crystal with Photochromic Group 1-menthone Applied as Reflective Polarizer.
Yu-Jen Chan 1 , Hsin-Hsien Fu 1 , Yu-Der Lee 1
1 Chemical Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractThis study is about fabricating a reflective polarizing film using dimethacrylate monomer and commercial nematogen (Merck E7) with photochromic chiral compound (1-menthone derivative) to form polymer-stabilized chiral nematic phase. Due to the unique helical structure, chiral nematic liquid crystal could reflect light of the same handedness and the wavelength equal to the pitch length of the chiral nematic liquid crystal. However, the reflection band is limited by the intrinsic birefringence. In this study, photochromic compound with chiral centers is introduced to adjust the reflection band by different exposure dose, and the structure is fixed by the polymeric network. This system could exhibit potential use in industry.
9:00 PM - BB5.7
Novel PH-thermosensitive Gel Adsorbents for Phosphoric Acid.
Takehiko Gotoh 1 , Takuya Arase 1 , Shuji Sakohara 1
1 Department of Chemical Engineering, Graduate School of Engineering, Hiroshima University, Higashi Hiroshima Japan
Show Abstract9:00 PM - BB5.8
Structural Colored Membrane without Dependence.
Yukikazu Takeoka 1 , Masaki Honda 1 , Takahiro Seki 1 , Masahiko Ishii 2 , Hiroshi Nakamura 2
1 , Nagoya University, Nagoya Japan, 2 , Toyota Central R&D Labs., Inc., Nagoya Japan
Show AbstractVisual information via the multimedia such as television, the internet, and now cellular telephone with a built-in wide screen is an invaluable source to gain an understanding of world events and meaningful information. People sometimes need such information from an outside location to ensure a precise response to the problem facing. It would be convenient to have mobile devices with a paper-like display on such an occasion. A variety of research and development projects regarding full-color paper-like display modules for seeing digital information outdoors are moving forward. The reflective modules for paper-like display must be one of the encouraging candidates, because such reflective displays can be clearly seen even under bright sunlight or dimly lit environments with contrast that is the same as newsprint, and can be available as energy-saving devices. However, to establish a reflective full-color display with wide viewing angle, the angle dependence of color becomes a major issue. Here we report that the condensed hydrogel particles aqueous suspensions display angle-independent structural colors. The structural colors are no longer brilliant color that can be seen from gemstone opal, but are no less remarkable. We anticipate that these angle-independent structural colored suspensions can be used to develop full-color paper-like displays.
9:00 PM - BB5.9
Fabrication of Mechanically Improved Hydrogels Using a Movable Cross-linker Based on Vinyl Modified Polyrotaxane.
Abu Imran 1 , Yukikazu Takeoka 1 , Takahiro Seki 1 , Toshiyuki Kataoka 2 , Masatoshi Kidowaki 2 , Kohzo Ito 2
1 Molecular Design and Engineering, Nagoya university, Nagoya, Aichi, Japan, 2 Department of Advanced Materials Science, Graduate School of Frontier Sciences,, The University of Tokyo, Kashiwa, Chiba, Japan
Show AbstractPolyrotaxane is a supramolecule consists of a larger number of macrocycles. In a sparse polyrotaxane the macrocycles can slide and rotate through the long polymer axle and the bulky end groups of the polymer prevent the dethreading of macrocycles. This fascinating characteristic of polyrotaxane have already been exploited for syntheses of various smart materials, for instance, molecular tubes,sliding gels etc. In this study, we focused on the use of polyrotaxanes as cross-linkers in syntheses of polymer gels with intriguing mechanical properties. We used sparsely dispersed polyrotaxanes (PR), consisting of α-cyclodextrin derivatives-rotors, which are threaded onto a long poly (ethylene glycol) axle (MW=35000 gmol-1) with an inclusion ratio of about 29% and are trapped by capping with bulky end groups 1-adamantanamine, as building blocks to make novel cross-linkers. The hydroxyl groups of α-CDs were modified by isocyanate monomer through the formation of a stable carbamate bond to obtain the polyrotaxane-based hydrophobic and hydrophilic type cross-linkers, MPRs. Polymer gels were fabricated by using the MPRs as cross-linkers and thermosensitive N-isopropylacrylamide (NIPA) as a monomer, which yielded transparent, very soft, flexible and mechanically improved rotaxane-NIPA (RN) gels. The superiority of the RN gels was compared with typical NIPA (TN) gels prepared by using N,N’-methylene-bis-acrylamide as a cross-linker. The RN gels and TN gels, which exhibited similar degree of swelling in water and DMSO were used for rheometric analysis. The RN gels were found to have much smaller storage modulus, E’ and loss modulus, E’’ values at the whole frequency ranges. This is indication of very soft nature of the RN gels. When the frequency is applied to the gel, the poly(NIPA) chains inside the gel network squeezes enough; but due to the sliding and rotating ability of the MPRs in the RN gel, the poly(NIPA) chains can gradually equalize its tension. In water, the gel exhibits sharp volume phase transition around the lower critical solution temperature (LCST) of NIPA. When the temperature of the gel rises above the LCST of poly(NIPA), the RN gel shrinks isotropically without any bubble formation, and the rate of volume phase transition is very fast. The movable cross-linked polymer networks allow the poly(NIPA) chains to relax under deformation. In contrast, the fixed cross-linked networks of the TN gels can not avoid the localization of the stress to a short poly(NIPA) chains and soon the gel looses its mechanical integrity. The TN gels always exhibit strong hysteresis during shrinking, while the use of the MPRs cross-linkers completely eliminates the hysteresis of typical poly(NIPA) gels through the movement of polymer networks. An increase in the amount of cross-linkers or increase in temperature results in increases in both E’ and E’’ in water as well as in DMSO i.e. the softness or hardness of the RN gel may, therefore, be well controlled.
Symposium Organizers
Zhongyang Cheng Auburn University
Qiming Zhang The Pennsylvania State University
Siegfried Bauer Johannes-Kepler University Linz
Debra A. Wrobleski Los Alamos National Laboratory
BB6: New Materials and Characterization
Session Chairs
Thursday AM, December 04, 2008
Grand Ballroom (Sheraton)
9:00 AM - **BB6.1
Design of Responsive Conducting Polymers.
Timothy Swager 1
1 Chemistry, MIT, Cambridge, Massachusetts, United States
Show Abstract9:30 AM - BB6.2
Nanorod Alignment and Reshaping in Block Copolymer Films.
Russell Composto 1 , Yu Liu 1 , Michael Hore 1
1 Materials Science and Eng., University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractTo control their unique electrical and optical properties, one-dimensional metallic/semiconductor nanoparticles need to be aligned and assembled within a host material. In our research, we investigated the assembly of gold nanorods (NRs) in films of a symmetric diblock copolymer, poly(styrene-b-methyl methacrylate), PS-b-PMMA. The NR length and diameter was 42nm and 13nm, respectively. The NRs were grafted with a short PEG-brush (5kg/mol). During solvent annealing, the NRs become oriented as the PS-b-PMMA chains assemble into a parallel lamellar morphology. The NRs are selectively sequestered and confined in the PMMA domains, which are narrower than the NR length, due to the favorable interaction between the PEG brush and PMMA block. This confinement orients 71% of NRs within ± 5° of the lamella plane. This route to produce alternating layers containing conducting NRs separated by dielectric domains has the potential for fabricating self-assembled nanodevices. The thermal stability and reshaping of the NRs in films as well as their unique optical properties will also be discussed.
9:45 AM - BB6.3
Bio-active Polymer Fibers for Environmental Remediation.
Ying Liu 1 , Miriam Rafailovich 1 , Ram Malal 2 , Daniel Cohn 2 , Dev Chidambaram 3
1 MSE, SUNY at Stony Brook, Stony Brook, New York, United States, 2 , Casali Institute of Applied Chemistry The Hebrew University of Jerusalem, Jeruslem Israel, 3 , Environmental Science Department, Brookhaven National Laboratory, Upton, New York, United States
Show Abstract Although microbes have been used in industrial and niche application for ages, successful immobilization of microbes while preserving the desired functionality has been elusive. Such a functionally bioactive system is expected to have several applications. This article addresses the use of Pluronic127 dimethacrylate (Pluronic127: PEO99-PPO67-PEO99 triblock polymer (PEO: Polyethylene oxide and PPO: Polypropylene oxide)) nanofibers to encapsulate three industrially relevant microbes, namely, Pseudomonas Fluorescens, Zymomonas Mobilis, and Escherichia Coli. The presence of bacteria inside the fibers was confirmed by fluorescence microscopy and scanning electron microscopy (SEM). Encapsulated microbes managed to survive the electrospinning process. Not only were the encapsulated microbes viable for several days, they maintained their functionality. Furthermore, we have created a cross-linked microbe encapsulated polymer material for the first time. Thus we report a novel process to create an insoluble microbe encapsulated active matrix. The present results demonstrate the potential of electrospinning process for the encapsulation and immobilization of living bacteria while maintaining their activity. This study has wide ranging implications in the creation and use of such novel biohybrid materials for applications such as sensors, biofuel production and environmental remediation.
10:00 AM - BB6.4
Studies of Structural Heterogeneities in Temperature and Voltage Responsive Hydrogels through Single Particle Tracking.
Paul Braun 2 , Paul Bohn 3 , Lindsay Elliott 1
2 Materials Science and Engineering, University of Illinois, Urbana-Champaign, Champaign, Illinois, United States, 3 Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana, United States, 1 Chemistry, University of Illinois, Urbana-Champaign, Champaign, Illinois, United States
Show Abstract10:15 AM - BB6.5
The Use of Surface Analytical Methods for Development of Anti-fouling Films by Surface Initiated Atom Transfer Radical Polymerization (SI-ATRP.
Douglas Gilliland 1 , Giacomo Ceccone 1 , Wilhelm Kulisch 1 , Pascal Colpo 1 , Francois Rossi 1
1 Institute for Health and Consumer Protection, Joint Research Center of the European Commission, Ispra(Va) Italy
Show Abstract10:30 AM - BB6.6
Tuning Polymer Brush Composition and Architecture for Reversible Adsorption and Modulation of Surface Reactivity.
Sarah Lane 1 , Zhifeng Kuang 1 , Shafi Arifuzzaman 2 , Steve Diamanti 1 , Jan Genzer 2 , Barry Farmer 1 , Rajesh Naik 1 , Richard Vaia 1
1 Materials and Manufacturing Directorate, Air Force Research Labs, Wright-Patterson AFB, Ohio, United States, 2 Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractPolymer brushes have been shown to be an excellent surface for the immobilization of proteins or other biomolecules for applications such as enhancing cell attachment or inhibiting biofilm formation. Through post-polymerization modification of poly(2-hydroxyethyl methacrylate) (PHEMA) brush, we examine the impact of brush architecture, chemical composition and environmental responsivity of the brush on the efficacy of covalently coupled enzymes. The PHEMA brushes, made using the grafting from approach, were activated with N’N’-disuccinimidyl carbonate (DSC), rendering the surface reactive towards alpha-terminal amines. The desired reactant (enzyme, small molecules or polymers) could be bound across the entire surface or patterned using reactive soft-lithography, as confirmed by XPS and SEM. Enzymes, such as horseradish peroxidase (HRP-C), are bound directly to the DSC activated brush through the lysine residues at the surface of the protein, as elucidated by computational modeling. Following enzyme immobilization, residual succinimide pendants could be further modified with amine-terminated thermoresponsive polymers, such as poly(N-isopropyl acrylamide) (PNIPAM) to create a complex brush architecture consisting of a PHEMA base with a mixture of enzyme and PNIPAM pendants. The responsive nature of the PNIPAM is envisioned to enable modulation of the enzymatic activity using the collapsed and expanded form of the pendant to regulate diffusivity of reactants and products in the vicinity of the enzyme.
10:45 AM - BB6.7
Phosphatidylinositol 4,5-bisphosphate is a Ligand of HCV NS5A and Mediates Viral Genome Replication.
Nam-Joon Cho 1 2 , Choongho Lee 1 , Phil Pang 1 , Curtis Frank 2 , Jeffrey Glenn 1
1 Division of Gastroenterology, Stanford University, Stanford, California, United States, 2 Chemical engineering, Stanford University, Stanford, California, United States
Show AbstractPhosphoinositides (PIs) are important mediators of intracellular signaling and membrane trafficking pathways. More recently, PIs have also been recognized as playing important roles in the subcellular localization of PI-interacting proteins which bind PIs via a variety of structural motifs. Here we discovered a novel role for phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) as a key mediator of genome replication for hepatitis C virus (HCV), an important worldwide cause of liver disease. We adapted the technique of quartz crystal microbalance with dissipation (QCM-D), wherein PtdIns(4,5)P2-containing polymerized liposomes deposited on quartz crystal nano sensors were allowed to interact with peptides derived from the N-terminal amphipathic helix (AH) of the HCV nonstructural protein 5A (NS5A) and the binding kinetics studied in real time. In particular, the NS5A AH was found to specifically bind polymerized liposomes containing PtdIns(4,5)P2 with a Kd of 4.4 uM. PIP-2 binding induced a significant conformational change in the AH. A pair of positively-charged lysine residues within the AH was found to be critical for mediating both PIP-2 binding and RNA genome replication. Finally, treatment with neomycin, a ligand of PIP-2, specifically inhibited HCV replication in a dose-dependent fashion. Together, these results demonstrate the first example of phosphoinositides-mediating viral genome replication, and suggest the potential for novel anti-HCV strategies.
11:30 AM - BB6.8
Fluorescence on Polymer-metal Interface using Pyrene as a Molecular Probe.
Yuehua Cui 1 , Tocarra Cecil 1 , Weijie Lu 1
1 Department of Chemistry, Fisk University, Nashville, Tennessee, United States
Show AbstractUnderstanding of the interactions and interfacial structure between polymer and metal is a major challenge. The fluorescent probe molecules can be inserted into the interface regions, and the changes in the fluorescence spectra can be directly corresponded to the interfacial interactions at the molecular and atomic levels. The fluorescence emission peaks resulted from the pyrene at the interface between pyrene/glass were at 514 nm and 517 nm at room temperature and annealing at 60oC, respectively. However, the fluorescence emission peaks at 514 nm were quenched and the fluorescence emission peak at 527 nm was enhanced in the samples of P3HT/Py/Metal at room temperature (Metal = Au, Ag, Cu, Ni, and Al), except for the Ti. For P3HT/Py/Metal samples under annealing conditions, the pyrene fluorescence emission peaks in the range of 513-517 nm were reduced but the peaks in 526-529 nm were increased. These phenomena are explained by molecular orbits theory and a mechanism of electrons transfer from metals to P3HT on molecular level is suggested.
11:45 AM - BB6.9
High-density Conducting Polymer Nanowire Arrays: Fabrication Based on Self-assembled Block Copolymer Nanolithography and a Sensor Application.
Yeon Sik Jung 1 , Woo Chul Jung 1 , Harry Tuller 1 , Caroline Ross 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractThe development and progress in the field of conductive polymers has great promise for many different applications such as optoelectronic devices, field effect transistors, and chemical or biological sensors. Furthermore, better device performance is often achieved by miniaturizing the feature sizes down to the nanoscale regime. The development of high-performance molecular nanoelectronic devices will therefore benefit from a simple, economic way to fabricate nanoscale features from functional organic materials such as layers of conducting, insulating, or light-emitting macromolecules. Block copolymer nanolithography is a promising method, with the advantages of large area coverage and compatibility with pre-established top-down patterning technologies. We previously reported the formation of defect-free and robust nanoscale line patterns from poly(styrene-b-dimethylsiloxane) (PS-PDMS).[1] Cylindrical morphology block copolymer films were spin-coated over silicon substrates patterned with shallow trenches, and solvent-annealed to facilitate ordering of the PDMS cylinders. The total molecular weight was 45.5 kg/mol, and the volume fraction of PDMS was 33.5%, providing a pattern with 35 nm periodicity. Treatment with an oxygen plasma removes the PS leaving oxidized PDMS cylinders, 15 nm wide, that provide robust etch masks for subsequent pattern transfer into poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) conducting polymer thin films. A two-terminal chemiresistor vapor-sensing device was fabricated by depositing Au electrodes on top of the PEDOT:PSS nanowires. The nanowire patterns showed an ethanol vapor sensing performance by generating response signals whose magnitude is proportional to the vapor pressure of ethanol. Moreover, the nanowire device was more sensitive than an equivalent unpatterned film. This result indicates the conservation of the molecular structure and properties of the PEDOT:PSS during harsh reactive ion etching processes. These well organized conductive polymer nanowire arrays may be useful for nanoscale organic device components such as interconnect lines or nanoelectrodes for high-density and high-performance nanodevices or electrochemical cells.[1] Jung, Y. S.; Ross, C. A. Nano Letters 2007, 7, (7), 2046-2050.
12:00 PM - BB6.10
Response of Fluorescence Thiophene based Conjugated Polymers on Exposure to Vapors of Aromatic Nitro Compounds.
Robinson Anandakathir 1 , Abhishek Kumar 1 2 , Ignaty Leshchiner 1 , Jayant Kumar 1 2 , Daniel Sandman 1 3 , Rudolph Faust 3
1 Center for Advanced Materials, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 2 Physics, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 3 Chemistry, University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show Abstract12:15 PM - BB6.11
A Generalizable Click Chemistry Approach to the Nano-Engineering of Biocompatible Thin Films.
Georgina Such 1 , Christopher Ochs 1 , Cameron Kinnane 1 , Angus Johnston 1 , Brigitte Stadler 1
1 Chemical and Biomolecular Engineering, University of Melbourne, Parkville, Victoria, Australia
Show AbstractThe design of new biomedical approaches in areas such as drug or gene delivery requires the development of sophisticated materials with tailored and specific properties, which are targeted to a particular application. Layer-by-layer (LbL) assembly is a well-studied, versatile and robust technique for fabricating such tailored materials. Covalently bound LbL films offer advantages over the conventional methods of assembly such as hydrogen bonding or electrostatics, due to increased stability and the ability to use a wider range of polymers. Click chemistry has generated significant interest recently as a new highly efficient method of covalent bonding. The most documented example is the CuI-catalyzed variant of the Huisgen 1,3 dipolar cycloaddition. There are numerous advantages to combining click chemistry with LbL assembly. Firstly, the reaction is simple, highly efficient and works effectively in water. The click moieties can also be easily incorporated onto a range of different materials including polymers, proteins or drugs without affecting other functionality present. Unlike traditional LbL approaches this method can be used to design films with either like-charged or non-charged materials, the latter being particularly important for biomaterials. Finally the triazole linkages formed in this reaction are extremely stable to hydrolysis, oxidation or reduction. In this research we have developed a general approach to LbL assembly using click-functional materials. The versatility of the approach was demonstrated by designing a range of single component films and capsules based on responsive polymers such as poly(acrylic acid), degradable biopolymers such as poly(L-glutamic acid) and low-fouling polymers such as poly(N-vinyl pyrollidone). These materials were also combined to form stratified materials with optimum characteristics for biomedical applications. The simple, efficient and general nature of the click approach, coupled with high stability, flexibility to combine a range of different materials and the ability to post-functionalize, provides exciting new opportunities for designing advanced and responsive click materials for use in therapeutic and diagnostic applications.
BB7: New Materials and Characterization
Session Chairs
Thursday PM, December 04, 2008
Grand Ballroom (Sheraton)
2:30 PM - **BB7.1
Left-hand Properties of Conductive-fiber Filled Epoxy.
Zhuo Xu 1 , Xuezhong Wen 1 , Feng Xie 1 , Xiaoyong Wei 1 , Shaobo Qu 1 , Xiaoqing Wu 1
1 electronic material research Lab. , Xi'an Jiaotong University, XI'an, Shaanxi, China
Show AbstractThe permittivity and permeability of composite filled with randomly-distributed conductive fibers in different parameters are investigated in this talk. The permittivity of such composites is negative near the resonance frequency, the resonance properties of permittivity such as resonance frequency and resonance amplitude etc. can be modulated by the length, diameter and volume concentration of the fibers. According to the results obtained from such composite, a new structure of composite materials named reverse-sandwiched composite is proposed. It is composed of two epoxy layers filled with conductive fibers with in-plane random distribution and a pure epoxy layer between them. The experiment results show that the permittivity and permeability of composite materials are negative simultaneously in the same frequency band from 8.14GHz to 13GHz by choosing appropriate thickness of the center epoxy layer of the reverse-sandwiched composite. This new reverse-sandwiched composite has properties of left-handed material in microwave range and a good advantage in manufacturing left-handed materials more easily.
3:00 PM - BB7.2
Nano-scale Sculpting on Polymers Using Focused Ion Beam,
Myoung-Woon Moon 1 , J.-h. Han 2 , E. k. Her 3 , K.-r. Lee 1 , K. h. Oh 3 , Ashkan Vaziri 4
1 Future Fusion Technology Research Laboratory, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Materials Science & Technology Research Division, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 3 Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 4 , Northeastern University, Boston, Massachusetts, United States
Show AbstractWe have recently showed that ordered wrinkles can be created on the surface of polymers using focused ion beam irradiation. In this talk, we provide an overview of the techniques developed for controlled creation of nanoscale wrinkling patterns on the polymer surface using focused ion beam. Moreover, examples of applications of focused ion beam for creation of various structural features on the surface of the polymers will be illustrated. Specific attention will be made to application of these techniques to polyimide, where peculiar one-dimensional and two-dimensional ripple structures can be fabricated using focused ion beam. Some of the key experimental challenges for precise fabrication of these surface structures will be discussed. Finally, the applications of the developed techniques in various multidisplinary applications including microfluidics, flexible electronics, biosensors, tissue engineering and regenerative medicine will be illustrated.
3:15 PM - BB7.3
Stochastic System Identification of the Compliance of Conducting Polymers.
Priam Pillai 1 , Ian Hunter 1
1 Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractConducting polymers such as polypyrrole, polythiophene and polyaniline are currently studied as novel biologically inspired actuators. The actuation mechanism of these materials depends upon the motion of ions in and out of the polymer film during electrochemical cycling. The diffusion of ions into the bulk of the film causes the dynamic compliance (or modulus) of the material to change during the actuation process. The mechanism of this change in compliance is not fully understood as it can depend on many different factors such as oxidation state, solvation of the film and the level of counter ion swelling. In-situ measurement of the compliance transfer function of polypyrrole as a function of charge is difficult since the compliance depends upon the excitation frequency as well as the electrochemical stimulus. Pytel et al (Polymer vol 49 pg 2008-2013 (2008)) studied the effect of the changing elastic modulus in-situ at a fixed frequency. In this study we describe a technique to measure the compliance transfer function of polypyrrole as a function of electrochemistry. A voltage input and a simultaneous stress input is applied to polypyrrole actuated in neat 1-butyl-3-methylimidazolium hexaflourophosphate. The stress input is stochastic with a bandwidth of 30 Hz and it allows us to compute the compliance transfer function of polypyrrole as function of the electrochemistry. Our studies show that the low frequency compliance changes by 50% as charge is injected into the polymer. The compliance changes reversibly as ions diffuse in and out of the film which indicates that the compliance depends upon the level of counter ion swelling.
3:30 PM - BB7.4
Thermomechanical Characterization of (Qua)ternary Thiol-ene/Acrylate Polymers for Photolithography and Shape Memory Applications.
Scott Kasprzak 1 , Blanton Martin 2 , Tulika Raj 3 , Ken Gall 1 4
1 Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 4 Materials Science & Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractIn our study, we investigate a class of polymers that have a potential use in both photolithography and shape memory use, namely thiol-ene polymers. Thiol-ene polymers are superior to acrylates in that they do not suffer from oxygen inhibition during polymerization, have a later gel point, have little shrinkage, and can be polymerized without photoinitiator. These qualities are due to the polymerization reaction itself, which differs substantially from the acrylate mechanism. We used various thermomechanical characterization techniques, such as dynamic mechanical analysis (DMA), along with more qualitative estimations to evaluate the potential of thiol-ene polymers to supplement acrylates in the library of polymers that are used for shape memory or photolithography purposes. We were interested in how the reaction mechanism is affected by various mixtures of constituent monomers, and how that related ultimately to the properties of the final material. The ternary mixtures we studied consisted of both a linear thiol and –ene monomer constituent, and either a tetrafunctioanl thiol or trifunctional –ene crosslinker. We found that thiol-ene polymers resulting from ternary mixtures can have a very broad range of properties and that processing them is less labor-intensive than processing acrylate mixtures. However, the thiol-enes do suffer from drawbacks, some of which are easily overcome: they are malodorous in monomer form; they have the propensity to undergo a so-called “dark reaction,” whereby the constituents polymerize without an external stimulus; and the glass transition temperatures are, almost without exception, sub-ambient. Transition temperatures for the thiol-crosslinked polymers ranged from -41.4 C to -15.72 C at 10 and 100 thiol-end-mol% crosslinker, respectively, and the -ene-crosslinked polymers’ transition temperatures ranged from -39.25 C to 35.14 C at 10 and 100 –ene-end-mol% crosslinker. Rubbery moduli for the same materials ranged from 0.05 MPa to 9.725 MPa for the thiol-crosslinked polymers and from 1.62 MPa to 14.89 MPa for the –ene-crosslinked networks. The low transition temperatures eliminated these pure ternary materials from use as typical shape memory materials. Therefore, we added a difunctional acrylate with a Tg of 63 C to the ternary mixtures at different concentrations, resulting in various quaternary mixtures that resulted in polymers exhbiting higher transition temperatures and rubbery moduli than the ternary thiol-ene polymers.
4:15 PM - BB7.5
Surface Phenomena in Control of Nanofiber Morphology in Conducting Polymers.
Sumedh Surwade 1 , Xinyu Zhang 1 , Vineet Dua 1 , Sanjeev Manohar 1
1 , University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show AbstractThe bulk synthesis of nanowires of electronically conducting polymers is typically achieved thorough chemical oxidative polymerization of the corresponding monomers. Single-solvent, non-template approaches are the most convenient to use that usually involve changing the synthetic parameters during the induction period of the reaction to affect a dramatic granule-to-fiber change in bulk polymer morphology, e.g., adding small amounts of oligomers or surfactants, adding nanofiber seeds, increasing the reaction temperature, diluting the reaction mixture, etc. Several mechanisms have been proposed, e.g., balance between primary and secondary nucleation processes, dimer-assisted polymer growth, intermediacy of rod-like intermediates, and double-layer driven rod-like growth. In this study we show that the phenomenon is driven primarily by surface phenomena and specifically, the build up of intermediate species on the surface of the reaction vessel and/or other inert surfaces during the induction period prior to bulk polymer precipitation. Nanowire polymer growth in solution is triggered by rod-like species present on the surface of the reaction flask and depending on the hydrophobic/hydrophilic properties of surface coatings the granule-to-fiber morphology can be completely reversed. These findings are consistent with our earlier nanofiber seeding mechanism for promoting nanowire growth, i.e., it is the overall shape of the intermediate species that is the primary factor in control of bulk polymer morphology. The phenomenon is general and can be extended beyond conducting polymers to classical organic polymers.
4:30 PM - BB7.6
Facile Synthesis of Elastic Aerogels and Xerogels from Methyltrimethoxysilane (MTMS).
Kazuyoshi Kanamori 1 , Kazuki Nakanishi 1 , Teiichi Hanada 1
1 Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto Japan
Show AbstractFor decades, transparent silica (SiO2) aerogels have been intensively studied due to their attractive properties such as low refractive index, excellent thermal insulation, and low dielectric constant etc. The silica aerogels are usually prepared from water glass or silicon alkoxide such as tetraalkoxysilane that is a typical precursor of the sol-gel method. However, poor mechanical properties and complicated production procedure have been preventing aerogels from large-scale industrial production and extended applications. Particularly, supercritical drying (SCD) is the most complicated and expensive process that should be avoided as far as possible. Further, if the seriously fragile property is improved, both production and handling of aerogels become much easier. For the purpose of improving the mechanical properties, we applied methyltrimethoxysilane (MTMS) as a single precursor in the sol-gel method to obtain organic-inorganic hybrid aerogels and xerogels. Although using MTMS as a single precursor results in macroscopic phase separation and inhomogeneous gelation in most cases, here we report a successful preparation of transparent monolithic methylsilsesquioxane (MeSiO1.5) aerogels with improved mechanical properties by effectively suppressing macroscopic phase separation.A cationic surfactant cetyltrimethylammonium bromide (CTAB, or chloride CTAC) or a nonionic poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F127, EO108PO70EO108) was used to suppress macroscopic phase separation. Also, urea was used to raise the solution pH during condensation reaction of MTMS by being hydrolyzed into carbon dioxide and ammonia. This accelerates gelation so that the solution will be solidified prior to macroscopic phase separation. Thus a starting solution containing appropriate amounts of MTMS, water, acid catalysis, surfactant and urea was allowed to gel by a one-pot reaction.Resultant aerogels obtained from supercritical drying exhibited good optical transparency (~80%) and a unique mechanical property. Upon uniaxial compression, the aerogel showed the “spring-back” behavior; the aerogel was compressed up to ~80% in linear, and then recovered almost completely after unloading. This elastic behavior implies that the gels can spring-back against the compression stress that is also exerted during the conventional evaporative drying. Thus we conducted the evaporative drying using several kinds of low surface energy solvents. The resultant “xerogels” show high optical transparency, and bulk density is also found to be as low as corresponding aerogels dried by SCD. The pore properties and morphologies of aerogels and xerogels were characterized utilizing FE-SEM, nitrogen sorption, small-angle X-ray scattering etc. and found that aerogels and xerogels are structurally comparable. This approach may open the way to the easy and low-cost aerogel production without using supercritical drying.
4:45 PM - BB7.7
Aromatic Polyurea for High Temperature High Energy Density Capacitors
Yong Wang 1 , Xin Zhou 1 , Minren Lin 2 , Baojin Chu 2 , Shengguo Lu 2 , Qiming Zhang 1 2
1 Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania, United States, 2 Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractWe investigate aromatic polyureas which can be fabricated in the form of thin films through CVD. It was found that the polymer possesses a flat dielectric response (k~ 4.2 and loss <1%)) to more than 200 oC. The frequency-independent dielectric properties in the investigated frequency range(1kHz~1MHz), low conductance, low dissipation factor (~0.005), high breakdown strength (>800MV/m), high energy density (>12J/cm3) and high efficiency suggest this polymer can be a good candidate material for high temperature energy storage capacitors. Breakdown strength was analyzed with Weibull model over a broad temperature range (25 oC ~180 oC). Experimental results indicate that aromatic polyurea is more like a nonpolar linear dielectric material because of its highly cross-linked structures. The experiment results further show that this polymer maintains its high performance even at high temperatures.
5:00 PM - BB7.8
Processing, Morphological Development and Mechanical Properties of Hybrid Polymer Nanomaterials.
Sanjeev Shrivastava 1 , I. Singh 1
1 Instrument Design Development Centre, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India
Show Abstract5:15 PM - BB7.9
Designing Molecular Devices for Diffusion of Small Charged Molecules.
Nihan Yonet-Tanyeri 1 , Rachel Evans 1 , Huilin Tu 1 , Paul Braun 1
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractQuasi-two dimensional poly(oligoethylene glycol) acrylate polymer brush based molecular conduits have been designed with the goal of regulating and controlling the diffusive transport of ionic, e.g. Ca ions and protons, and molecular, e.g. organic dyes, species along predefined 2-D pathways. The transport of these chemical species has been examined by both fluorescence and laser scanning confocal microscopy. The polymer brushes were formed through microcontact printing of an initiator, followed by surface-initiated Atom Transfer Radical Polymerization (SI-ATRP). SI-ATRP enables both 2-D patterning with a resolution of about 1 micrometer, and control over the resultant polymer brush thickness (which was varied from 10-100 nm). A hydrophilic poly(oligoethylene glycol) acrylate brush was selected because of its potential to dissolve a wide range of hydrophilic species. The transport of fluorescent species can be directly imaged. The Ca ion and proton transport is studied by first introducing ion specific fluorescent indicators into the brush. Then, as the ion of interest diffuses through the brush the indicators fluoresce. We have demonstrated that the various species of interest diffuse much more rapidly along the predefined pathway than along the bare (polymer brush free) regions of the substrate, demonstrating that diffusive conduits for molecular transport can indeed be formed.
5:30 PM - BB7.10
Effect of Sonication on Mechanical Properties of Nanocomposites.
Xue Sha 1 , Andrey Beyle 1 , Christopher Ibeh 1
1 , Pittsburg State University, Pittsburg, Kansas, United States
Show AbstractIn many cases smart materials are produced by dispersing nanoparticles with specific physical properties in polymer matrix. Impregnating of nanoparticles into a polymer can tailor not only its physical but also mechanical properties. The way of mixing the nanoparticles with the polymer is the most critical issue. Sonication is one of the best approaches to disperse the nanoparticles into the matrix material, degas it, and break the intermolecular bonds in particle aggregates thoroughly. Better mixing can provide higher strength and stiffness whereas bad mixing will decrease those properties. Physical properties are also depending on the quality of dispersion. However, sonication is not the analog of simple mechanical stirring, it is changing physical and mechanical properties of the material constituents also. The influence of technological parameters of sonication on mechanical properties of nanoclay (as a model of nanoparticles with more specific physical properties) impregnated in vinyl esters was studied. The synergy of some parameters such as sonication time, temperature and concentration of nanoclay was found. The role of each effect was estimated by using two level three-factor factorial design of experiment equation which is modified mathematical design of experiments technique; it is observed that concentration plays the main role. The effects of sonication time and sonication temperature individually exhibit relatively less influence. However, the significant synergetic effect from combination of them was observed.The kinetics study shows that sonication significantly changing kinetics of materials solidification and their mechanical properties not only after curing but also even after additional postcuring at elevated temperature.
5:45 PM - BB7.11
Designing Robust Omniphobic Surfaces.
Anish Tuteja 1 , Wonjae Choi 2 , Joseph Mabry 3 , Gareth McKinley 2 , Robert Cohen 1
1 Department of Chemical Enginerring, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Mechanical Enginerring, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Air Force Research Laboratory, Edwards Air Force Base, Edwards, California, United States
Show AbstractSuperhydrophobicity, i.e. the ability of various surfaces to cause water droplets to bead up and roll off their surface, is a common observation in nature. Two of the most famous examples of natural superhydrophobic surfaces are lotus leaves and duck feathers. The synergistic effects of surface texture and relatively low surface energy enable duck feathers to trap pockets of air underneath droplets of a high surface tension liquid like water (
γlv = 72.1 mN/m) and form a stable composite solid-liquid-air interface that resists wetting. However, the feather’s natural surface chemistry and texture are insufficient to withstand the decrease in free energy arising from the spreading of lower surface tension fluids such as oils or alcohols. Thus, as is tragically evident after an oil-spill, low surface tension liquids like gasoline and rapeseed oil (
γlv = 35.7 mN/m) completely wet the surface of a duck feather.
Designing and producing textured surfaces that can resist wetting by such low surface tension fluids has been a significant challenge in materials science, and no examples of such materials exist in nature. In this work we develop various surfaces possessing re-entrant texture1 that can support composite solid-liquid-air interfaces, even with extremely low surface tension liquids such as pentane (γlv = 15.7 mN/m) - the lowest surface tension alkane in liquid state at atmospheric pressure. Further, to aid the systematic engineering of non-wetting surfaces, we develop four dimensionless design parameters that allow us to provide an a priori estimation of both the apparent contact angles, as well as the robustness of the composite interface.
Guided by these design parameters, we produce electrospun polymeric (poly methyl methacrylate - PMMA) fiber mats containing extremely low surface energy, fluoroalkyl-substituted silsequioxane molecules (fluorodecyl POSS).1,2 The low surface energy of fluorodecyl POSS molecules, as well as their small size, enables them to migrate (bloom) to the fiber-air interface during the electrospinning process. As a consequence, electrospun fibers (with radius ~ 500 nm) containing as low as 5 vol% POSS can display extremely high contact angles (> 150°) and support a robust composite interface with a wide range of polar and non-polar liquids. We suggest the term ‘omniphobic’, i.e. surfaces that resist wetting by all liquids, to describe such surfaces. In addition, we describe a simple ‘dip-coating’ process that imbues omniphobicity to any surface possessing re-entrant texture by conformally coating the substrate with PMMA – fluorodecyl POSS blends. We further show that it is possible to easily tune the surface wettability of these substrates via control of the chemical composition of the dip-coating solution or through simple mechanical deformation.
References:
1.Tuteja, A. et al., Science, 318, 1618-1622 (2007).
2.Mabry, Joseph M. et al., Angew. Chem. Int. Ed. 47 (22), 4137-4140 (2008).
BB8: Poster Session
Session Chairs
Siegfried Bauer
Qiming Zhang
Friday AM, December 05, 2008
Exhibition Hall D (Hynes)
9:00 PM - BB8.1
Macromolecular Scaffolding: Polyisocyanopeptide Based Multi-chromophoric Arrays: Unraveling the Relationship between Nanoscale Architecture and Function in Materials for Organic Electronics.
Paolo Samori 1 2 , Vincenzo Palermo 2 , Erik Schwartz 3 , Chris Finlayson 5 , Ya-Shih Huang 5 , Matthijs Otten 3 , Andrea Liscio 2 , Kalina Paneva 4 , Klaus Muellen 4 , Richard Friend 5 , Roeland Nolte 3 , Alan Rowan 3
1 Institut de Science et d'Ingénierie Supramoléculaires, Université Louis Pasteur de Strasbourg, Strasbourg France, 2 Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Bologna Italy, 3 Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen Netherlands, 5 Cavendish Laboratory, University of Cambridge, Cambidge United Kingdom, 4 , Max-Planck Institute for Polymer Research, Mainz Germany
Show Abstract9:00 PM - BB8.10
Ceramic-polymer 0-3 Composites with High Dielectric Constant.
Xiaobing Shan 1 , Lin Zhang 1 , Peixuan Wu 1 , Canran Xu 1 , Zhongyang Cheng 1
1 Materials Research and Education Center, Auburn University, Auburn, Alabama, United States
Show AbstractPowers of high-dielectric-constant ceramic CaCu3Ti4O12 (CCTO) were dispersed into poly(vinylidene fluoride – trifluorethylene) [P(VDF-TrFE)] to fabricate the ceramic-polymer 0-3 composites using solution casting method and followed by a hot-pressing technique. It is found that the composites exhibit a very high dielectric constant, about 510 at room temperature and 1240 at 95 °C at 1 kHz. The uniformity of composite is a key to achieve the high dielectric constant. The process to prepare a uniform composite was investigated. The Cole-Cole analysis of the dielectric response from the composites indicates that the interfacial layer plays an important role for the observed high dielectric constant.
9:00 PM - BB8.11
Crystalinity Properties of Carbon Nanotube- Polyvinylidene Fluoride Compostes.
Xiaobing Shan 1 , Peixuan Wu 1 , Lin Zhang 1 , Zhongyang Cheng 1
1 Materials Research and Education Center, Auburn University, Auburn, Alabama, United States
Show AbstractSingle-wall and multi-wall carbon nanotube blends (0 to 0.5 vol% )with polyvinylidene fluoride (PVDF) have been prepared using solution cast method and characterized. By acid treatment, it has been observed that nanotube has been well functionalized and uniformly dispersed into the polymer. X-ray diffraction analysis coupled with differential scanning calorimetry (DSC) has revealed that carbon nanotube alters the crystallinity of PVDF and thereby enhances the β-phase in PVDF. Experimental results have demonstrated that enhancement of β-phase is a function of carbon nanotube concentration.
9:00 PM - BB8.12
Synthesis and Characterization of Free-Standing Two-Dimensional Polymers Made of Host Molecules.
Kangkyun Baek 1 , Youngkook Kim 1 , Gyeongwon Yun 1 , Dongwoo Kim 1 , Juseok Kang 2 , Chan Gyung Park 2 , Kimoon Kim 1
1 National Creative Research Initiative Center for Smart Supramolecules and Department of Chemistry, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractTwo-dimensional (2D) polymers are of great interest for use in microelectromechanical devices in the form of sensors or actuators that endure repeated elastic deformation. They may also be used as permselective membranes or as scaffolds for the organization of nanoparticles. Several methods to produce such thin polymer sheets have been reported, such as polymerization of lipid bilayers, self-organization of block copolymers, cross-linking of polymer brush on a patterned surface, and polymerization at the oil–water interface. Although the previous synthetic approaches have produced cross-linked sheets, they all need either a preorganized structure or template to shape a 2D structure, and furthermore they require multistep processes. Here we describe the direct synthesis of free-standing 2D polymers made of host molecules cross-linked in the lateral directions in solution without any aiding agents. The cross metathesis of a rigid, disk-shaped host molecule, cucurituril (CB[6]), with polymerizable allyl groups at the periphery in DMF using Grubbs’ catalyst directly produced free-standing 2D polymers, which have been characterized by FT-IR, SEM and TEM studies. The resulting 2D polymers with a wide range of sizes from a few micrometers to a few millimeters appear to be flexible and thin enough to be wrinkled, rolled and broken by the electron beam under SEM and TEM observations. We have also grown such 2D polymers on a TEM grid floated at an oil-water interface. Furthermore, the surface of the 2D polymers can be easily modified through host-guest interactions by taking advantage of molecular cavities, readily accessible at the surface, and their strong affinity toward polyamines.
9:00 PM - BB8.13
Strain Sensitivity in Ion-implanted Polymers.
Giovanni Di Girolamo 1 , Marcello Massaro 1 , Emanuela Piscopiello 1 , Emanuela Pesce 1 , Ciro Esposito 1 , Leander Tapfer 1 , Marco Vittori Antisari 2
1 FIM, ENEA, CR Brindisi, Brindisi Italy, 2 FIM, ENEA, CR Casaccia, Rome Italy
Show AbstractPolymer-based materials are very attractive for the realization of pressure, strain and mechanical sensor devices. Here, the ion implantation process was used to modify the near-surface polymer structure in order to fabricate ultra-thin conducting films in inert polymers and to tailor the surface electrical properties for strain-gauge applications. Polycarbonate substrates were implanted at room temperature with low energy Cu+ ions of 60 keV, at 1 μA/cm2 and with doses in a range from 1x10^16 to 1x10^17 ions/cm2. The nanocomposite surfaces were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), optical absorption spectroscopy and electrical conductivity. XRD and TEM measurements show that Cu nanocrystals are formed at ion doses of 1x10^16 ions/cm2 and are located at about 50nm-80nm below the polymer surface in accordance with TRIM calculations (projected range of 75nm and straggling of 20nm). Optical absorption spectra show a surface plasmon resonance (SPR) at 2eV in accordance with the formation of Cu nanoparticles. For doses of 5x10^16 ions/cm2 the XRD and TEM results indicate the formation of a continuous nanocrystalline Cu film and a well pronounced SPR peak is observed. However, for higher doses (1x10^17 ions/cm2) damaged and structurally disordered film are obtained and the SPR peak is smeared out. In addition, electrical conductivity measurements clearly show a reduced electrical resistance for the sample implanted with a doses up to 5x10^16 ions/cm2, while higher doses (1x10^17 ions/cm2) are detrimental for the electrical properties probably due to the induced damage. The dependence of electrical resistance on surface load (up to 3MPa) was evaluated during tests of compression and bending. A significant linear variation of the electrical resistance with the surface load (or bending) was found (load increase → electrical resistance decrease) and can be related to the changes of spatial distribution of Cu nanoparticles in the subsurface film. Furthermore, only a very small hysteresis effect could be noticed. It should be also noted that the subsurface nanocrystalline Cu films remain stable in time without oxidizing and preserving the characteristic mechanical and electrical properties. Our results clearly show that these surface nanocomposite layers in polymers are promising structures for the fabrication of sensitive strain sensors embedded in polymers. Furthermore, these structures can be fabricated on micro- and nanoscale and can be easily incorporated in other microelectronic devices.
9:00 PM - BB8.14
A New Type of Display Device Based on Remote Swelling and Collapse of a pH Responsive Microgel.
Joseph Cook 1 , Jason Riley 1
1 Department of Materials, Imperial College London, London United Kingdom
Show AbstractA microgel particle is a colloidally sized cross-linked polymer particle that can respond to an external stimulus such as pH, temperature or ionic strength. Microgel particles have been synthesised with the weak base 2-vinylpyridine as the principal monomer and 0.5% by weight divinylbenzene as a cross-linker using surfactant free emulsion polymerisation. The particles swell from the as-prepared diameter of around 140 nm to a maximum diameter of around 780 nm when the pH is reduced to below 4.5. A dispersion of the collapsed particles scatter light efficiently and so appear milky white and opaque. The swollen particles appear largely transparent because they are too large to scatter the wavelengths of visible light efficiently and they consist mainly of water and so there is little contrast between the refractive indices inside and outside of the particle. This difference in opacity could form the basis for a new display device, where partitioned sections containing dispersions of the particles are placed in front of a black background and different sections are set to the collapsed and swollen states to produce a black and white image. The possiblity of using the conductive polymer poly(aniline) to modify the pH of a dispersion has been investigated. A film of poly(aniline) was deposited onto a platinum wire mesh and the electrode held at potentials between -0.2 V and +0.8 V vs. Ag/AgCl with a counter electrode also consisting of Ag/AgCl. The pH of 10 cm3 of a solution of hydrochloric acid was modified between around pH 3 and around pH 6 over a period of hours. Swelling and collapse was successfully induced in 103 of a 0.2% by weight dispersion of poly(2-vinylpyridine) microgel particles over a period of several minutes, although reversibility and consistency are at present proving difficult.
9:00 PM - BB8.15
Design of MEH-PPV/Alq3 Indicator-dosimeter for Neonates During Blue-light Phototherapy Treatments.
Giovana Ferreira 1 , Cláudia Barbosa de Vasconcelos 1 , Rodrigo Bianchi 1
1 Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil
Show AbstractBlue-light phototherapy is the most widespread treatment of neonatal jaundice since it devoid off all complications of an invasive procedure and presents the same spectral emission as the electronic absorption spectrum of bilirubin. It acts in the sense to further reducing bilirubin level of infant’s serum concentration and, thus, to prevent serious complications, as kernicterus. Although most jaundice in newborn infants is not serious and it is easily and relatively inexpensive to be controlled with efficient phototherapy, two factors may alter the rate of decline in serum bilirubin level of neonates: the spectrum and the total dose of light delivery. As a consequence, the need for an effective management of the radiation doses planning before treatment of jaundice is therefore obvious. In order to design a novel device for this purpose, the luminescent and organic materials, such as the (aluminum-tris(8-hydroxyquinoline)) - Alq3 and the poly[(2-methoxy-5-hexyloxy)-p-phenylenevinylene – MEH-PPV, commonly employed in green and orange-red light-emitting diodes, respectively, appear here as good candidates for color indicator-dosimeters of blue-light radiation since they are highly susceptible to photoxidation processes which dramatically change their color and photoemission spectra, and the rate of these changes solutions can also be altered by manipulations of organic solutions. This result reveals, on the one hand, the low reliability of organic devices, and on the other reflects the possibility to design and develop dosimeters where the effects of non-ionizing radiation on the optical properties of organic materials are more important than improving the luminance and lifetime of the light-emitting diodes made from them. In this work, we described blue-light dosimetry studies using a novel dosimeter based on poly[(2-methoxy-5-hexyloxy)-p-phenylenevinylene] / (aluminum-tris(8-hydroxyquinoline)) - MEH-PPV/Alq3 systems that easily survey on radiation doses absorbed by newborns in the treatment of neonatal jaundice. Optical absorption and photoluminescence measurements have been done on MEH-PPV/Alq3 solutions. We show that there is a visible response that covers the electronic absorption of bilirubin, and hence this material is applicable for manages the radiation doses planning before treatment of jaundice of neonates. The results show that the material presents a gradation of color from orange to yellow clearly, while its peak position emission shifts from orange-red (λmax = 571 nm) to green (λmax = 540 nm) with the radiation exposure time. The rate of these changes can be altered by manipulations of organic solution concentration and they are usually slow (from 2 h to 8 h), suggesting these color and emission changes can be used to design an indicator-dosimeter in order to represent easily the radiation exposure time usually used in management of neonatal jaundice. This work was sponsored by FAPEMIG, CAPES and CNPq from Brazil.
9:00 PM - BB8.16
Improvement of Blocking Force of IPMC by Electroplating Method and Optimizing Mobile Cations and Electrolytes.
Hyung-Kun Lee 1 , Nak-Jin Choi 1 , Sunkyung Jung 1 , Kang-Ho Park 1 , Jongdae Kim 1
1 , ETRI, Daejeon, 305-700, Korea (the Republic of)
Show Abstract9:00 PM - BB8.17
Characterization of the Charging and Long Term Performance of Cytop Electret Layers for MEMS Applications.
Ulrich Bartsch 1 , João Gaspar 1 , Oliver Paul 1
1 Department of Microsystems Engineering, University of Freiburg - IMTEK, Freiburg Germany
Show AbstractU. Bartsch, J. Gaspar, O. PaulMicrosystems Materials Laboratory, Department of Microsystems Engineering - IMTEK, University of Freiburg, GermanyResearch in the field of polymer electrets compatible with microelectromechanical systems (MEMS) is of great interest because of the potential application of these materials in electrostatic micro energy harvesting devices. The characterization of the performance of these materials as electrets as well as their compatibility with standard MEMS fabrication processes are therefore necessary for the implementation of these layers in actual micro devices.This work focuses on the electret properties of Cytop CTL-809M (Asahi Glass Co., Ltd., Tokyo, Japan), structured using thin film technology. The long term stability and influence of temperature on Cytop charged under different conditions are investigated. The charge storage capability of patterned Cytop is studied as well and mathematical models are developed.The fabrication of the samples starts with the deposition of a Cr/Au/Cr stack on top of a Pyrex substrate, followed by a multilayer of Cytop spun onto the metallization. The spin-coating steps can be repeated as many times as necessary to obtain the desired layer thickness. Thicknesses ranging from less than 1 µm to more than 20 μm can thus be achieved. A softbake at 100°C is performed after each spin-coating step. After deposition, the Cytop is hardbaked at 185°C for 60 min. Photolithography is then performed using AZ9260 resist from MicroChemicals. The Cytop layer is finally patterned by reactive ion etching with an etch rate of 0.74 μm/min.The Cytop layers are charged using a corona discharge setup that can be operated in constant current or constant voltage mode. The charged electrets are characterized using an electrostatic voltmeter (Model 279, Monroe Electronics) and a measurement setup that allows scanning over the electret surface with an adjustable measurement gap. Automated 1D and 2D scan routines of up to 16 chips are possible.The long term effects on the charge stability of the Cytop electret layers are investigated as a function of the corona grid voltage, temperature and duration of charging. The Cytop layers are still charged with at least 92% of their initial charge value 143 days after the corona procedure. No so called cross-over effect, that is a faster discharging of samples charged to higher potentials compared to less charged samples, is observed in the first 143 days. In addition, the sample temperature during the corona discharge has no visible effect on the charge stability during this period. In contrast, with increasing test temperature, the temperature induced discharge leads to a decrease of the surface potential.The charging characteristics of patterned electret lines strongly depend on the line width. Corresponding measurements and a model will be presented in the paper.
9:00 PM - BB8.18
The Melt Electrospinning of Polycaprolactone (PCL) Ultrafine Fibers.
Chitrabala Subramanian 1 , Samuel Ugbolue 1 , Steven Warner 1 , Prabir Patra 2
1 Materials and Textiles, UMass, Dartmouth, Massachusetts, United States, 2 Mechanical Engineering and Materials Science, Rice University, Hosuton, Texas, United States
Show AbstractElectrospinning is a technique of producing nanofibers from polymer solution/melt solely under the influence of electrostatic forces. Owing to the high surface area to volume ratio, nanofibers find wide applications in the filtration and biomedical field. Though great deal of research efforts have been directed towards solution electrospinning, focus on melt electrospinning has been limited. Melt electrospinning would be a cost effective and ecofriendly way of producing nanofibers. Successful production of nanofibers by electrospinning biodegradable polymer melts would benefit the biomedical field.In this research, we investigated the formation of nanofibers by melt electrospinning polycaprolactone (PCL). The effect of process parameters such as molecular weight, applied voltage, and electrode separation on the fiber diameter was studied experimentally. Controlling the process parameters could help increase the proportion of ultrafine fibers in the melt electrospun nonwoven mat. The velocity of the straight jets was in the range of 0.2-1 m/s. The melt electrospun fibers were characterized with respect to fiber diameter, distribution, mechanical properties and birefringence. Melt electrospun polycaprolactone fibers had a diameter distribution of the order of 5 -20 µm, with the least being 260 nm. Results of single fibers testing on Instron testing machine showed a mean tenacity of 1.2 g/den, initial modulus of 4.8 gf/den and extension-at-break of 190% for polycaprolactone. The birefringence of the melt electrospun fibers increased with decrease in fiber diameter. Different fiber morphologies were observed namely: cylindrical, fused, spiral fibers.
9:00 PM - BB8.19
Complex Impedance of PVDF Thin Films Containing BaTiO3 Nanoparticules.
Marcos Costa e Silva 1 , Seila Rojas 2 , Antonio Hernandes 2 , Rodrigo Bianchi 1
1 Departamento de Física, Universidade Federal de Ouro Preto, Ouro Preto, MG, Brazil, 2 Departamento de Física e Ciência dos Materiais, Instituto de Física de São Carlos, USP, São Carlos, SP, Brazil
Show AbstractIntensive investigations of piezo/ferroelectricity in polymers were sparked in 1969 with Kawaii's discovery of strong piezoelectric properties measured in uniaxially drawn and poled poly (fluoride vinylidene) – PVDF. Since its patent in 1948, PVDF was already known as a chemically inert "tough" plastic with a high dielectric constant. With the subsequent reporting of PVDF's piezoelectric properties in 1971, much work began for sensor and actuator devices on the other hands, when PVDF is associated with a piezoelectric ceramic it may result in a flexible ferroelectric material with interesting mechanical, electrical and/or thermal properties. In this work, we have investigate the complex impedance of PVDF and barium titanate – BaTiO3 nanocomposite as function of temperature and BaTiO3 contents in order to elucidate the role of the inorganic material in the polymer matrix. In order to understanding the contribution of both phases, the electrical characteristics of the films were analyzed making using of impedance spectroscopy measurements in the frequency range from 100 mHz to 32 MHz and also from room temperature to 200 οC. Moreover, the real and imaginary components of the complex impedance of PVDF/BaTiO3 are observed to obey a classical Davidson – Cole phenomenological approach behavior in which the BaTiO3 acts in the sense to decrease the relaxation time of the material and to increase their dielectrical permittivity. Some methods were used for analyses of impedance spectroscopy measurements. It is the case of Maxwell Garnet and Bruggeman models, both based on the Clausius – Mossotti equation for a dielectric medium in which the interaction between the particles (host medium) was neglected. However, we used here the model developed by Jayasundere and Smith to predict the dielectric permittivity of the nanocomposite since it deals with the nanoparticles interaction. In fact, each BaTio3 particle sparked in the PVDF matrix can be considered as a dipole which has strong influence on other inorganic particules. This work was sponsored by CNPQ and FAPEMIG agencies from Brazil.
9:00 PM - BB8.20
Long Lifetime Dielectric Elastomer Actuators under Continuous High Electromechanical Strain.
Wei Yuan 1 , Paul Brochu 1 , Soon Mok Ha 1 , Qibing Pei 1
1 Materials Science & Engineering, University of California, Los Angeles, Los Angeles, California, United States
Show Abstract9:00 PM - BB8.21
Fabication Of Conductive Polydiacetylene Nanocrystals By Chemical Doping.
Hitoshi Kasai 1 2 , Koichi Baba 1 , Shinohara Yoshikazu 1 , Shuji Okada 1 , Hiro Matsuda 3 , Hidetoshi Oikawa 1 , Hachiro Nakanishi 1
1 IMRAM, Tohoku Univ., Sendai Japan, 2 PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama Japan, 3 , National Institute of Advanced Industrial Science and Technology, Tsukuba Japan
Show AbstractPolydiacetylene (PDA) is a single crystal of fully-conjugated polymer, which is obtained by the solid-state polymerization of its diacetylene monomer. Because of highly ordered backbone structure of PDA, an attractive conjugated system for electronical-optical studies has been studied. One of the most interesting properties of PDA is the high value of charge carrier mobility (μ) in pristine PDA crystals (μ = 1∼10 cm/Vs). However, the pristine state of PDA crystals are nearly insulators, giving a low electrical conductivity (σ = ∼10<-12> S/cm). For the improvement of the electrical conductivity, several strategies have been reported. Recently, the maximum conductivity obtained in chemically doped PDA crystals was to be as high as σ = ∼10<-2> S/cm. One of the big issues in increasing the conductivity of PDA is in its rigid crystalline lattice, which prevents the dopant from penetrating into PDA bulk crystals. This was especially in 1,6-di(N-carbazolyl)-2,4-hexadiyne (DCHD).In this study, for overcoming the difficulty of chemical doping to PDA, we tried chemical doping into the PDA nanocrystals, because PDA nanocrystals are known to have a softened crystal lattice and a large surface area, compared with bulk crystals. As a result, we demonstrated almost the highest conductivity of chemically doped PDA ever reported. The electrical conductivity achieved was ca. (1.3 ± 0.8) × 10<-2> S/cm.
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Encapsulation of Gold Nanoparticles in Thermoresponsive Microgels.
Rafael Contreras-Caceres 1 2 , Ana Sanchez-Iglesias 1 , Isabel Pastoriza-Santos 1 , Jorge Perez-Juste 1 , Jessica Pacifico 1 , Antonio Fernandez-Barbero 2 , Luis Liz-Marzan 1
1 Physical Chemistry, University of Vigo, Vigo Spain, 2 Applied Physics, University of Almería, Almería Spain
Show Abstract9:00 PM - BB8.23
Stimuli-Responsive Polymer Nanocapsules.
Jiyeong Lee 1 , Eunju Kim 1 , Kimoon Kim 1
1 Department of Chemistry, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show Abstract9:00 PM - BB8.24
Electroactive Polymer Actuators.
Rafil Basheer 1 , Roy Kornbluh 2
1 , Materia Chemica LLC, Rochester, Michigan, United States, 2 , SRI International, Menlo Park, California, United States
Show AbstractBased on electric field-induced deformation of low elastic modulus polysiloxane elastomers with compliant electrodes, dielectric elastomer actuators can yield an extremely large strain with fast response time and a high electromechanical efficiency. This powerful electroactive response results from Maxwell stresses arising due to electric field pressure of free charges on the dielectric surface. Electrically actuated strain of over 100%, stress values of 3 MPa or more, response speed that can be as high as 20 kHz, and efficiency greater than 80% have been measured for such systems. For elastomers that are like polysiloxane in their elastic characteristics and low temperature properties, but have higher dielectric constant values and better tear strength, improvement in performance is predicted. By the incorporation of a proper proportion of the polyrizable cyano- or fluoro- functionalities as side groups in the desired elastomer, elastomers with higher dielectric constant values can be prepared. For silicone elastomers, this may be achieved through hydrosilylation reaction of an appropriate hydrosiloxane polymer and a cyano- or fluoro- containing vinyl compound. While this approach is expected to improve the performance of the actuator as a result of increasing the dielectric constant, it will not improve the low tear strength characteristics of the silicone elastomer. Materials with high tear strength values would allow actuator fabrication with a smaller film thickness, which would in turn improve the energy output. Alternative low modulus elastomers having similarly high dielectric constant values, yet possessing superior tear strength characteristics, were prepared from fluoroalkoxy- nucleophilic substitution of freshly prepared polydichlorophosphazene from the thermal ring-opening polymerization of phosphonitrilic chloride. By varying the proportion and structure of the mixed fluoroalkoxy substituents, it was possible to produce low Tg polyphosphazene elastomers having the desired dielectric and mechanical properties for optimum actuator performance. Here we will present data on the correlation between the structural and network parameters and the physical and engineering performance parameters for actuators made from a series of fluoroalkoxy substituted polyphosphazene elastomers.
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Hyper-Branched Architectures for Design of High Energy Density Dielectrics.
Meng Guo 1 , Theodore Goodson 1
1 , University of Michigan-Ann Arbor, Ann Arbor, Michigan, United States
Show AbstractHigh energy density capacitors operating at high frequencies are being developed for diverse power electronic and pulse power applications [1-2]. These new materials will enable the minimization in size and reduction in cost for next generation electronics. Organic high dielectric materials have great promise due to the possibility of high dielectric constant at higher frequencies and lower loss. They also offer advantages such as good flexibility, excellent tailor-ability, and good compatibility with existing microelectronics components [3]. Unlike ordinary linear polymers, hyper-branched architecture may provide enhanced dielectric response due to a hyper-electronic polarization [4-5]. In this contribution we show results of a phthalocyanine dendrimer system with a high dielectric constant of ~46 and a relatively low dielectric loss (<0.01) at 1MHz [5]. In our study, a group of novel hyper-branched copper phthalocyanine polymers were designed. The characterization of these materials including the capacitance, steady state adsorption and emission, transient absorption, time-of-flight mobility, atomic force microscopy and EPR spectroscopy will be presented. These results elucidate the mechanisms underlying the observed properties and demonstrate its connection with our structural design. Reference1. Chu, B. J.; Zhou, X.; Ren, K. L.; Neese, B.; Lin, M. R.; Wang, Q.; Bauer, F.; Zhang, Q. M. Science 2006, 334- 336.2. Guo, M.; Yan, X.Z.; Goodson III, T. Accepted by Adv.Mater.3. Goodson III, T. Acc .Chem. Res. 2005, 38 (2), 99-107.4. Yan, X. Z.; Goodson III, T. Phys. Chem. B, 2006, 110, 14667 -14672.5. Guo, M.; Yan, X.Z.; Young, K.; Teruaki, H.; Kakimoto, M.A.; Goodson III, T. J. Am. Chem. Soc. 2006, 128, 14820.
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Photo-mechanical Coupling in Polymer-carbon Nanotube Composites and Photoconductive Polymer.
Benjamin Fragneaud 1 , Jeffrey Kysar 1
1 Mechanical Engineering, Columbia University, New York, New York, United States
Show AbstractRecent studies have shown that composites made with a poly(dimethyl siloxane) (PDMS) matrix that contains carbon nanotubes (CNT) exhibit both a photo-mechanical coupling as well as a photo-conductive coupling when exposed to a visible white light. The photo-mechanical coupling manifests itself as an effective expansion or contraction upon exposure to light, depending upon the applied prestrain. The photo-conductive coupling indicates that the electrical conductivity increases with exposure to white light. To study these phenomena, we prepared various composites with different CNT concentrations (0 vol. % to 2.5 vol. %) in the non-photo-conductive PDMS matrix. In addition, we prepared specimens with the polymer poly(vinyl carbazol) (PVK) which is known to be photo-conductive in the absence of any carbon nanotubes, and showed that the PVK itself also exhibits a similar photo-mechanical actuation. Both materials were characterized by various experimental methods such as coupled photo-conductive and photo-mechanical analyses, photo-thermal mechanical analyses, and bulge test, among others. A model is developed that predicts the photo-mechanical actuation as a function of applied prestrain. Furthermore, the results obtained with the pristine PVK suggest that theoretical speculation concerning the origin of the photo-mechanical coupling can be partially attributed to changes of the macromolecule dimensions. The goal of this research is to correlate the electronic structure of such materials to the photo-mechanical coupling properties.
9:00 PM - BB8.27
Grafted Polymeric Nanostructures Patterned Bottom-Up by Colloidal Lithography and Initiated Chemical Vapor Deposition (iCVD).
Nathan Trujillo 1 , Sal Baxamusa 1 , Karen Gleason 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambrige, Massachusetts, United States
Show AbstractMaterials patterning through non-conventional lithography can reduce the cost of patterning fine structures when compared to traditional nanofabrication techniques such as photolithography. Colloidal lithography is a popular non-conventional process which involves the use of two–dimensional self-assembled monolayer arrays of colloidal nanoparticles as masks for “top-down” techniques such as etching or sputtering. Initiated Chemical Vapor Deposition (iCVD) is a low-energy, one step, solvent-free process for producing functional polymeric thin films. Unlike other vapor phase techniques for producing polymer films, which tradeoff between film functionality and growth rate, iCVD is a mild process which produces polymers with structure analogous to those synthesized in solution. Furthermore, iCVD is a surface controlled process and this affords unprecedented opportunity for producing polymer brushes patterned through a colloidal template by grafting to substrates with dangling vinyl bonds. The adhesion contrast between the polymer/substrate interface and the polymer/particle interface allows the patterns to be generated without the need for an aggressive solvent. This “bottom-up” process is a simple technique for creating well-ordered arrays of functional patterned polymeric nanostructures, as small as 25 nm, with a robust polymer/substrate interface. We will present a generic process for patterning different functional polymers, using colloidal nanoparticle masks over various length scales.
9:00 PM - BB8.28
Electric Force Microscopy Investigation of Localized Electric Field Enhancement in Electrostrictive Polymer Nanocomposite Materials.
Aaron Sellinger 1 , Hilmar Koerner 1 , Ramanan Krishnamoorti 2 , Zoubeida Ounaies 3 , Richard Vaia 1
1 Materials and Manufacturing Directorate, AFRL, Wright-Patterson Air Force Base, Ohio, United States, 2 Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, United States, 3 Aerospace Engineering, Texas A&M, College Station, Texas, United States
Show AbstractPolymers that exhibit electromechanical coupling underlie many futuristic concepts, ranging from autonomous robots and aerial vehicles to micro-fluidics and energy harvesting. Unfortunately, achieving significant strains at reasonable applied voltages in many of these materials has proved problematic, severely limiting their performance. An emerging solution to this challenge focuses on exploiting the remarkable properties of nanostructured materials by incorporating nanoparticles into polymer-based piezoelectric and electrostrictive films. Recent efforts have shown that many nanocomposites exhibit substantially greater mechanical deformation at lower applied voltages than their respective polymer matrix alone. This improved performance has been partially attributed to enhancements in the local electric field at inclusion-matrix interfaces. Local field enhancements may cooperate to promote a reduction in the effective voltage required to induce macroscale deformation, thereby improving electromechanical efficiency. In an effort to explore local electric field enhancement in greater detail, electric force microscopy (EFM) was performed on nanocomposites that exhibit enhanced electrostrictive response, such as unpoled polyvinylidenefluoride (PVDF) doped with single-walled carbon nanotubes (SWNTs), clay platelets, and VO2 nanoparticles in both rod and spherical forms. Samples were cross-sectioned and characterized at applied voltages ranging from 0 to 10 V to investigate the local electric field distribution as a function of applied field strength.
9:00 PM - BB8.29
Multiple Quantum NMR of Structure-Property Relationships in Synthetic and Aged Silicones and Nanocomposites.
Julie Herberg 1 , Robert Maxwell 1 , Sarah Chinn 1 , Ticora Jone 1 , Sonia Letant 1 , Theodore Baumann 1 , Andrew Saab 1
1 , llnl, Livermore, California, United States
Show AbstractUnderstanding of the role of the filler-polymer interface in material behavior is a key step in developing rational structure-property relationships and predictive models for lifetime performance. 1H relaxation and multiple quantum NMR methods are proving to be versatile and sensitive tools for assessing not only changes in molecular level speciation, but also in the network structure. We use these methods to understand the changes that occur at the polymer-filler interface and in the network structure in families of micron- and nanometer scale silica filled polydimethylsiloxane (PDMS) based elastomers. These experiments have proven capable of separating time-dependent changes in the mobility of both the bulk polymer network and the surface associated chains and have provided in depth insight into potentially life limiting aging phenomena for these materials. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract # W-7405-ENG-48.
9:00 PM - BB8.3
Direction Sensitive Deformation Sensing with Epoxy Nanocomposites Sensors.
Samuel Buschhorn 1 , Malte Wichmann 1 , Jan Gehrmann 1 , Lars Boeger 1 , Karl Schulte 1
1 Institute of Polymer Composites, Technische Universität Hamburg-Harburg, Hamburg Germany
Show Abstract9:00 PM - BB8.30
The Spectroscopic Investigation of Electrospun Polymer Nanofibers Containing Photochromic Diarylethenes.
Carl Giller 1 , Andrea Bianco 2 , Chiara Bertarelli 2 , Giuseppe Zerbi 2 , D. Chase 3 1 , John Rabolt 1
1 Materials Science and Engineering, University of Delaware, Newark, Delaware, United States, 2 Department of Chemistry, Materials, and Chemical Engineering, Politecnico di Milano, Milan Italy, 3 , Dupont Central Research and Development, Wilmington, Delaware, United States
Show Abstract Diarylethenes are a unique family of photochromic compounds that exist in and can be reversibly switched between two different isomeric states displaying different physical and chemical properties. Upon irradiation of the “open” form, containing heterocyclic aromatic moieties, with UV radiation the molecule undergoes an intramolecular cyclization reaction resulting in the “closed form”, containing a conjugated backbone that has an electronic absorption band in the visible. The various objectives of this project all contain the underlying theme of incorporating these unique compounds into nonwoven electrospun fabrics that can find applications ranging from anti-counterfeiting and chemical sensors to new apparel. The first part of this study focuses on attempts to detect intermolecular aromatic interactions between the guest diarylethene and the host polymer by observing perturbations in both the electronic absorption and vibrational spectra of the diarylethene. A number of polymers with aromatic moieties including polystyrene, polycarbonate, poly(4-vinylbiphenyl), poly(vinyl phenol), poly(N-vinylcarbazole), and poly(4-chlorostyrene) were doped with varying quantities of an oligomeric diarylethene, c64b, in solution and electrospun into fibers spanning a wide range of sizes. FE-SEM was used to characterize the morphology of the system and diffuse-reflectance UV-Vis spectroscopy as well as FT-Raman scattering was employed to determine the degree of such interactions.The second part of this study is an attempt to discern whether or not the size of the polymer fiber has an effect on the photochemistry of the diarylethene. Nylon 6 polymer solutions were doped with another diarylethene containing a methoxy substituent, AM178, and electrospun into fibers having diameters spanning well over an order of magnitude, but with relatively narrow distributions. These fibers were characterized with the aforementioned analytical techniques to discern the extent of perturbations, if any, in the photochemistry of the dye.The third and final part of this study follows up on recent evidence1 indicating that small monomeric diarylethenes can be molecularly oriented in electrospun fibers. Because the cause of the molecular orientation remains unresolved, an in-depth study was carried out in which electrospun polymers with varying degrees of polarity were doped with diarylethenes also with different degrees of polarity to determine the extent of the orientation of the small molecules and the cause thereof. Polymers studied included polystyrene and poly(ethylene oxide). FE-SEM, polarized FT-IR spectroscopy, and Polarized UV-Vis spectroscopy were used to analyze the electrospun systems and help clarify the origin of the orientation.1. A. Bianco, G. Iardino, A. Manuelli, C. Bertarelli, and G. Zerbi. ChemPhysChem, 2007, 8, 510-514.
9:00 PM - BB8.31
Unexpected Thermal Responsive Behavior of Well-defined Poly(N-isopropylacrylamide) Brush Synthesized by Surface-initiated Atom Transfer Radical Polymerization.
Hiromasa Suzuki 1 , Yukikazu Takeoka 1 , Takahiro Seki 1 , Taisuke Kawamoto 2 , Hisashi Haga 2 , Kazushige Kawabata 2
1 Graduate School of Engineering, Nagoya University, Nagoya Japan, 2 Graduate School of Science, Hokkaido University, Sapporo Japan
Show AbstractIn recent years, surface-initiated graft living radical polymerization has received much attention to attain smart controls of surface properties such as wettability, geometry, viscoelasticity and so on. In particular, stimuli-sensitive polymer brushes have many potential applications in the biotechnology or biomedical filed. Poly(N-isopropylacrylamide) (PNIPA), one of the most widely-studied thermoresponsive polymer, has lower critical solution temperature (LCST) around 32 oC in water. In this study, we prepared well-defined PNIPA brushes on the surface of silicon-wafers, and characterized these thermal responsivities.The PNIPA brushes were fabricated by surface-initiated atom transfer radical polymerization (ATRP) as following procedures: 1) A chloro-terminated (initiator) SAMs was formed onto a silicon-wafer. 2) NIPA was polymerized from the chloro-terminated SAMs by ATRP in the presence of a free initiator. The chain lengths and the surface densities of the PNIPA brushes were determined by GPC and AFM. Thermal responsive behavior of PNIPA brushes was evaluated by AFM, FT-IR and air-bubble contact angle measurement in water. From GPC and AFM analyses, it was confirmed that the polymerization of NIPA proceeded in a living fashion, and PNIPA densely grafted on the silicon wafers (0.5 chains / nm2). In the air-bubble contact angle measurement in water, we found that the contact angle increased around 32 oC, which means unexpectedly that the PNIPA brush surface became hydrophilic over the LCST. This behavior was different from the surface wettability behavior of generally observed PNIPA surfaces. This behavior is expected to occur by the changes in the surface morphology of the brush by dehydration. We are planning to conduct AFM measurements in water and the work is in progress.
9:00 PM - BB8.32
Colloidosomes: ``Smart" Materials for Biomedical Applications.
Rachel Rosenberg 1
1 Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractColloidosomes have a wide range of applications including cell encapsulation, imaging and diagnostics, and drug delivery. They consist of an aqueous polymer core with a shell of colloidal particles adsorbed to the surface by electrostatic interactions. The distribution and packing of the colloidal particles determine the pore size. Poly (N-isopropylacrylamide) (PNIPAAm) and alginate hydrogels are used as two different aqueous gel scaffolds, synthesized via microfluidics. The shells consist of packed polystyrene spheres which are functionalized to yield the appropriate charge. Temperature and pH sensitive polymers allow the packing of the colloidal particles to be tuned. Modifying the pore size can be particularly useful in drug delivery applications that require localization.
9:00 PM - BB8.33
Surface Activity of a New Emerging Class of Ionic Nanoparticles.
Jason Fang 1 , Haris Retsos 1 , Robert Rodriguez 1 , Emmanuel Giannelis 1
1 Materials Science and Engineering , Cornell University, Ithaca , New York, United States
Show AbstractNanoparticle-based ionic materials (NIMs) offer exciting opportunities for research at the forefront of science and engineering. NIMs are hybrid particles comprised of a charged oligomeric corona attached to hard, inorganic nanoparticle cores. Because of their hybrid nature, physical properties –rheological, optical, electrical, thermal - of NIMs can be tailored over an unusually wide range by varying geometric and chemical characteristics of the core and canopy and thermodynamic variables such as temperature and volume fraction. On one end of the spectrum are materials with high core content, which display properties similar to crystalline solids, stiff waxes, and gels. At the opposite extreme are systems that spontaneously form particle-based fluids characterized by transport properties remarkably similar to simple liquids. In this poster I will present our efforts to synthesize NIMs and mainly discuss their surface properties. In particular I will discuss our work on preparing smart surfaces using NIMs.
9:00 PM - BB8.34
Fabrication of Anti-Reflection Coatings on Polymer Substrates using Spray Coating.
Kenneth Etcheverry 1 , Anindarupa Chunder 1 , Lei Zhai 1
1 , University of Central Florida, Orlando, Florida, United States
Show Abstract9:00 PM - BB8.35
Introduction of Polysiloxane Nanoparticles and Polysiloxane Star Polymers into Thermoresponsive Poly(N-isopropylacrylamide) (PNIPAAm) Hydrogels.
Yaping Hou 1 , Jonathan Burkes 1 , Allen Bulick 2 , Mariah Hahn 2 , Melissa Grunlan 1
1 Biomedical Engineering, Texas A&M University, College Station, Texas, United States, 2 Chemical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractMaterials which reversibly switch from a hydrophilic to hydrophobic state in aqueous media in response to an external stimulus are of interest for creating “smart” or “intelligent” biomedical materials. Poly(N-isopropylacrylamide) (PNIPAAm) hydrogels are known to become more hydrophobic when they reversibly switch from a water-swollen to a shrunken (deswollen) state at temperatures above the volume phase transition temperature (VPTT) of ~33 ○C. Thus, it has been previously shown that cells cultured on PNIPAAm surfaces above the VPTT are released as confluent cell sheets upon cooling below the VPTT (i.e. cell sheet engineering). Extending the utility of PNIPAAm hydrogels as robust cell-releasing materials for tissue culture substrates, anti-fouling coatings, or “self-cleaning” implanted sensor membranes requires improvement of their poor mechanical properties as well as tailoring the changes in surface hydrophilicity/hydrophobicity. We have introduced variable levels of polysiloxane colloidal particles (ave. diam. ~220 nm) and methacrylated star poly(dimethylsiloxane) (PDMSstarMA) each into PNIPAAM hydrogel matrix to form “nanocomposite” and “hybrid” hydrogels, respectively, using photochemical cure methods. The resulting changes in swelling, morphological, mechanical, and surface properties of these hydrogels were characterized. The release of mouse smooth muscle precursor (10T1/2) cells from these hydrogel surfaces upon cooling from 37 ○C to 25 ○C was evaluated.
9:00 PM - BB8.36
Microstructure and Dielectric Properties of CCTO-P(VDF-TrFE) Nanocomposites.
Lin Zhang 1 , Xiaobing Shan 1 , Peixuan Wu 1 , Zhongyang Cheng 1
1 Materials Research and Education Center, Auburn university, Auburn, Alabama, United States
Show AbstractCeramic/polymer nanocomposites, CaCu3Ti4O12 (CCTO) nano-powders filled into P(VDF-TrFE) copolymers matrix, have been fabricated by solution casting method. The CCTO ceramic powders were prepared by traditional solid state reaction and reduced to a relative uniform nano-size by high energy ball milling system. In order to achieve better uniformity, different hot pressing configurations and conditions have been studied. All samples with 10vol.%~50vol.% CCTO fractions were annealed at 125°C to improve the crystallinity of P(VDF-TrFE). The morphology of the fracture surface of samples was examined using SEM. For the nanocomposites with 50 vol.% CCTO, the dielectric constant can reach 60 at 1 kHz with a dielectric loss of 0.05. It is found that the nanocomposites exhibit a much lower dielectric loss and a smaller dielectric constant than micro-size composites.
9:00 PM - BB8.37
Electroactive Polymer Motors for Aerospace Applications.
Keith Rebello 1 , Margaret Darrin 1 , Jerry Krill 1
1 , The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, United States
Show AbstractElectric motors and combustion engines are widely used in commercial industries but are not appropriate for all applications. In particular aerospace applications can benefit from lightweight motors which can operate at high altitudes such as in the stratosphere layer of the atmosphere or in the atmosphere of a different planet, such as Mars. For example, there is use for a class of balloon airships which can support a payload at high altitude at a relatively fixed geographic location for extended periods of time. To maintain geographic position in the presence of high altitude winds, where the air has low density, a motor and transmission are useful that can turn a station-keeping propeller that is both large and slowly rotating. Another class of vehicles includes spacecraft and satellites, which need light, efficient technology, for example to extend arms and solar panels or to open or close compartments. Probes delivered by these vehicles—like the Mars rovers or submersible autonomous vehicles for the exploration of extraterrestrial seas also could use lightweight and efficient motors and transmission elements. A prototype electroactive polymer (EAP) dielectric motor was built from spring roll elements. By utilizing direct electric control of the artificial muscle elements, the need for complex and bulky gearboxes and transmissions were eliminated. The EAP materials allow for the fabrication of motors much lighter than their conventional counterparts with low radar cross sections with the capability to operate at high altitudes and oxygen free environments. Performance results and lessons learned for future developments will be presented.
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Study of Electrospun Fiber Nanocomposites of Poly(vinylidene fluoride) with Organically Modified Silicate Nanoclay.
Lei Yu 1 , Peggy Cebe 1
1 Physics, Tufts University, Medford, Massachusetts, United States
Show AbstractPoly(vinylidene fluoride), PVDF, is a polar polymer that exhibits several crystallographic phases including the polar all-trans beta phase and non-polar alpha phase. Previously, our group showed that PVDF nanocomposites containing small amounts of organically modified silicates (OMS) formed beta phase crystals preferentially. In the present work, we report on electrospun fiber nanocomposites of PVDF with Lucentite, a synthetic smectite clay. We studied the fiber morphology, crystal polymorphism of PVDF electrospun with both Lucentite STN and SWN nanoclays, from dimethylacetamide solution. The STN form of Lucentite is organically modified with tri octyl methyl ammonium ions [(C8H17)3CH3N]+ contained between the layers of hectrite; SWN Lucentite has no organic modification. The addition of either type of Lucentite nanoclay has the effect to enhance the growth of the polar beta phase in the electrospun PVDF/Lucentite nanocomposite fibers. Other researchers reported that the addition of hygroscopic salt can enhance the beta phase in electrospun PVDF through formation of hydrogen bonds between fluorine and retained water. Our results indicate that there is another mechanism for the growth of beta phase, independent of whether clay is organically modified with ions. (Research supported by the Petroleum Research Fund of the American Chemical Society, grant 44149-AC7).
9:00 PM - BB8.39
Measurement of the Photomechanical Forces Exerted by Azobenzene Based Polymers.
Zahid Mahimwalla 1 , Christopher Barrett 1 , Yoshihiko Nagai 2
1 Chemistry, McGill University, Montreal, Quebec, Canada, 2 Physics, McGill University, Montreal, Quebec, Canada
Show AbstractThe reversible light induced isomerisation of the azobenzene chromophore is capable of powerful changes to properties of the host material. The photomechanical effect is such a change defined by reversible shape or volume transformations by the adsorption of light that cause significant macroscopic mechanical deformation of the host material.1 Azobenzene based materials have been shown to demonstrate in thin films a reversible relative extent of expansion of 0.6–1.6%2, macroscopic bending of samples3 and micron-scale surface mass transport4. If the full potential of such photomechanical changes for applications in photo actuators such as the light powered engine of Masiero et al5 is to be realized macroscopic forces exerted by the photoisomerization of azobenzene needs to be adequately characterized. Here we report our measurements of the photomechanical effects of a well known azobenzene polymer poly disperse red 1A (PDR1A) using atomic force microscopy. A tipless silicon cantilever was coated on one side with PDR1A and irradiated with green (514nm) light. Subsequent cantilever bending was measured using a red (628nm) laser. The force exerted by the polymer was measured to be 20 ± 6 *10-4 N/m, with a cantilever deflection of 30 ± 5 *10-6m. It was noticed during measurements that response time of the polymer varied with “wetness” of the sample. Investigations of the role of pump beam power, film thickness, irradiation duration and further studies on the effect of solvent and solvent content upon the photomechanical force exerted by the polymer are continuing.While the photomechanical effects and their limitations of published azobenzene based actuators have been characterized, work has yet to be done to characterize the influences of changes such as solvent content, film thickness, addition of chemical moieties etc. may have upon the photomechanical forces exerted by azobenzene based materials. We believe this work presents a step towards the general characterization of the macroscopic forces exerted by azobenzene based materials to realize their potential for uses in photo actuators. References:1. Barrett C. J., Mamiya J-i, Yager K.G., Ikeda T, Soft Matter, 2007, 3, 1249–12612.Yager K. G., Tanchak O. M., Godbout C., Fritzsche H., Barrett C. J., Macromolecules 2006, 39, 9311-93193.Yu Y., Maeda T., Mamiya J-i, Ikeda T., Angew. Chem. Int. Ed. 2007, 46, 881 –883,4. Yager K.G., Barrett C. J., Macromolecules 2006, 39, 9320-93265.Masiero S.,Lena S., Pieraccini S., Spada G. P., Angew. Chem. Int. Ed. 2008, 47, 3184 –3187
9:00 PM - BB8.4
Fabrication of an Electrochromic Device based on Polyaniline-poly(vinyl alcohol)-natural Polymer Blends.
Michael Ibrahim 1 , Maria Bassil 1 , Mario El Tahchi 1 2 , Joseph Farah 1
1 Physics, Lebanese University-Faculty of Sciences II, Beirut Lebanon, 2 , Smart-X sarl, Berytech Technology and health, Beirut, Damascus Road, Lebanon
Show AbstractSince the discovery of the first electrochromic (EC) material, the applications of conductive polymers have been developed and used especially in the 1990’s using organic or inorganic materials and polymers. These novel polymers are still under intensive research and development worldwide both in the academic world and in the chemical and electronics industries. During the electrochemical redox reaction, the electronic structure of an EC polymer is modified and its color changes reversibly. EC materials require low power or voltage and have a high transmission in the region of visible light. One of the applications of these properties is the “smart windows” using a layer of tungsten oxide WO3 which works as an EC material. Polyaniline (PANI), discovered over 150 years ago, is a good EC material with high electrical conductivity (in the range of 5 S/cm), simple to produce since it can be prepared chemically or electrochemically by the oxidation of aniline and has a good stability. Depending on the redox state, PANI can be pale yellow or dark green/black. PANI is used for packaging electronic products, integrated circuits, printed circuit boards and many other applications.Based on PANI, the fabrication of an EC flexible layer, which can be used as an EC device in houses and cars windows, is possible. The usage of insulating polymer provides good mechanical properties and the conducting polymer such as PANI provides good electrical conductivity. Relying on the properties of PANI, the present study consists of preparing blends of three polymers which are poly(vinyl alcohol) PVA, PANI and a natural polymer to produce an electrically conducting layers which can change their color by applying a low voltage, at the same time these layers will have the property of light polarizer. Thus the control of the transmission of these layers will be either by using the polarized light activity or based on the EC effect.[1] J. Stejskal and R. G. Gilbert, Polyaniline: preparation of a conducting polymer, Pure Applied Chemistry, Vol. 74, No. 5, pp. 857–867, 2002.[2] Peter Andersson, Magnus Berggren and Thomas Kugler, Switchable optical polarizer based on Electrochromism in stretch-aligned Polyaniline, Applied Physics Letters Vol. 83 No. 7, 2003.
9:00 PM - BB8.40
The Effect of Surface Localization of Fluorophores on Trace Explosive Detection using Fluorescence Quenching.
Ignaty Leshchiner 1 2 , Abhishek Kumar 1 3 , Jayant Kumar 1 3
1 Center for Advanced Materials, University of Massachusetts Lowell, Lowell, Massachusetts, United States, 2 Chemistry, Moscow State University , Moscow Russian Federation, 3 Physics, University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show Abstract9:00 PM - BB8.42
Controllable Nano-net Assembly on AAO Templates.
Zhixun Luo 1 , Yuanyuan Liu 1 , Yaobin Wang 1 , Hongbin Fu 1 , Ying Ma 1 , Jiannian Yao 1 , Boon Loo 2
1 Institute of Chemistry, Chinese Academy of Sciences, Beijing China, 2 Department of Chemistry, Towson University, Towson, Maryland, United States
Show Abstract9:00 PM - BB8.43
Ionic Electro-Active Polymer Electromechanical Actuators Constructed through Layer-by-Layer (LbL) Deposition.
Reza Montazami 1 4 , Vaibhav Jain 2 , Sheng Liu 3 , Minren Lin 3 , Qiming Zhang 3 , James Heflin 4
1 Materials Science and Engineering , Virginia Tech , Blacksburg , Virginia, United States, 4 Physics , Virginia Tech , Blacksburg , Virginia, United States, 2 Macromolecular Science and Engineering, Virginia Tech , Blacksburg , Virginia, United States, 3 Electrical Engineering, Pennsylvania State University, University Park, Pennsylvania, United States
Show Abstract9:00 PM - BB8.45
Patterning of Nano-Elements using Parylene-C Shadow Mask Technology.
Kyle Anstey 1 , Selvapraba Selvarasah 1 , Nidhi Shrivastava 1 , Ahmed Busnaina 2 , Mehmet Dokmeci 1
1 Electrical and Computer Engineering, Northestern University, Boston, Massachusetts, United States, 2 Mechanical Engineering, Northeastern University, Boston, Massachusetts, United States
Show Abstract9:00 PM - BB8.46
Synthesis of Thermoresponsive Copolymers Composed of Poly(ethylene oxide) and Poly(N-isopropylacrylamide).
Tatiya Trongsatitkul 1 , Bridgette Budhlall 1
1 Department of Plastics Engineering, University of Massachusetts, Lowell, Massachusetts, United States
Show Abstract9:00 PM - BB8.47
Bio-inspired Polymeric Surfaces with Responsive, High-Aspect-ratio Nanostructures.
Boaz Pokroy 1 , Joanna Aizenberg 1
1 School of Engineering and applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractNature is replete with examples of multi-functional materials, which often exhibit superior properties as compared to synthetic materials. The Gecko's feet that strongly adhere to almost any surface and allow the lizard to easily climb vertical walls, fish and amphibians have cilia on the surfaces of their bodies connected to a hair cell at their base that detect water flow and the glass fibers in the Venus's flower basket sponge that possess fiber optical properties as well as superior mechanical design, are just a few striking examples.Albeit all these examples seem to be very different from each other, it is noteworthy that they share a common structural feature: all these functional natural materials are comprised of high-aspect-ratio fibers.Inspired by these biological designs, we have developed a finely tunable, multifunctional, responsive, high-aspect-ratio, polymeric nanostructured material that exhibits a variety of properties, such as actuation/sensing, self-cleaning and self-assembly into different patterns.For this purpose, we utilized soft lithographical techniques used to replicate high-aspect-ratio structures in a variety of polymeric materials. The proposed technique makes it possible to control the geometry of the high-aspect-ratio pillars (tilt, length and 2D array lattice and symmetry). We show that we can also finely tune the stiffness of the replicated polymeric structures within four orders of magnitude (several MPa to a few GPa). The details of the fabrication technique and a range of possible applications of these “smart” surfaces will be discussed. 1. Submitted to Advanced Materials (2008).
9:00 PM - BB8.5
Ionic Polymer-Metal Composite with Fast Bending Speed and Large Displacement by Anisotropic Plasma Etching.
Nak-Jin Choi 1 , Hyungkun Lee 1 , Sunkyung Jung 1 , Kang-Ho Park 1 , Jongdae Kim 1
1 , Electronics and Telecommunications Research Institute , Daejeon Korea (the Republic of)
Show Abstract9:00 PM - BB8.6
Mechanical Properties of Organized Composite Polymer Microstructures.
Srikanth Singamaneni 1 , Sehoon Chang 1 , Ji-Hyun Jang 2 , Edwin Thomas 2 , Vladimir Tsukruk 1
1 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Department of Materials Science and Engineering and Institute of Soldier Nanotechnologies, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractModern applications involving microfabricated structures and microdevices based upon polymeric materials call for sophisticated engineered surfaces and interfaces tailored to control elasticity, plasticity, adhesion, chemical, and thermal properties. We demonstrate that organized, porous, polymer microstructures with continuous open nanoscale pores and sub-micron spacings obtained via interference lithography can be successfully utilized as ordered microcomposites. Examples presented here include porous matrices for the fabrication of binary, glassy-rubbery microcomposites with intriguing mechanical properties and ordered microstructures with a high level of energy dissipation and lattice-controlled fracturing. We demonstrate that organized porous microstructures with continuous open microscopic pores can be successfully utilized for the fabrication of binary organized microcomposites with intriguing mechanical properties, such as lattice-controlled crack propagation and high energy dissipation due to multiple failures of struts and rubbery domains. Such organized glassy-rubbery microcomposites can find novel applications, which require precise control of the mechanical elastic and plastic behavior at micro and nanoscale.
9:00 PM - BB8.7
Effects of Fiber-Reinforcement on the Thermomechanical and Mechanical Properties of Shape Memory Polymers.
Devatha Nair 1 , Neil Cramer 2 , Christopher Bowman 2 5 , Michael Lyons 1 , Bryan Rech 1 , Robin Shandas 1 3 4
1 Dept. of Mechanical Engineering, University of Colorado-Boulder, Boulder, Colorado, United States, 2 Dept. of Chemical and Biological Engineering, University of Colorado-Boulder, Boulder, Colorado, United States, 5 Department of Restorative Dentistry, University of Colorado Health Sciences Center, Denver, Colorado, United States, 3 Dept. of Pediatrics, Section of Cardiology, The Children’s Hospital / University of Colorado Health Sciences Center, Denver, Colorado, United States, 4 , Center for Bioengineering, Denver, Colorado, United States
Show AbstractShape memory polymers are a class of materials that can be programmed to respond to specific stimuli in their environment. By designing polymer systems that use body temperature as a trigger, it is possible to deliver shape memory polymer-based medical devices in a minimally invasive manner to the target location where, on being exposed to the temperature trigger, they can ‘switch’ to their final shape. Although it is possible to increase the tensile strength and modulus of the shape memory polymer by varying the formulation of the system, any increase in strength in the polymer is observed at the expense of a reduction in elongation of the system. An increase in the modulus and tensile strength of the base polymer without compromising the elongation of the system can result in a wider range of design, functionality and manufacturing options for the polymer. Utilizing a reinforced or composite shape memory polymer aids in the ability to manufacture shape memory devices without compromising the critical shape memory effect. Fiber-reinforced composites (FRCs) are often made for applications that call for high strength and stiffness in relation to weight. In general, this translates to a high tensile strength over a relatively large temperature range and a high modulus of elasticity, thereby increasing the manufacturing options for the material. A fiber reinforced polymer (FRP) composite is one in which the dispersed phase is a fiber and the matrix phase a polymer. The mechanical properties of Fiber Reinforced Polymers depend on the individual material properties and on the degree of division of the applied load between the two materials. The factors that work to improve the tensile strength of the composite include a strong interface between the matrix and the fiber, the presence of low stress concentration points and fiber orientation. This study examines longitudinally placed fibers in a polymer matrix loaded uni-axially along the longitudinal axis of the fiber. The fibers chosen for the study were based on their acceptability as proven biocompatible polymers. The purpose of this research is to tailor the thermomechanical and mechanical characteristics of an acrylic based shape memory polymer system to aid in the design and manufacture of Fiber-Reinforced shape memory polymer medical devices. We show that by reinforcing the base acrylic shape memory polymer with a range of biocompatible fibers, it is possible to considerably enhance the tensile strength and modulus of the composite without compromising the elongation of the base polymer, while maintaining its shape memory properties.
9:00 PM - BB8.8
Micro- and Nano-Scale Controlled Fabrication of Highly Ordered Polymer Composite Films.
Janine Nunes 1 , Libin Du 1 , Joseph DeSimone 1 2
1 Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States, 2 Department of Chemical Engineering, North Carolina State University, Raleigh, North Carolina, United States
Show AbstractThe soft lithography technique, Particle Replication in Non-wetting Templates (PRINT), is a viable approach to the fabrication of well-structured, multifunctional polymer composite films for materials with controlled electrical, optical and mechanical properties. PRINT utilizes perfluoropolyether (PFPE) elastomeric molds to generate ordered arrays of monodisperse, shape-specific particles. Implementing a layering PRINT approach results in the uniform dispersion of particles in a polymer matrix forming complex three dimensional architectures, where particles cannot aggregate. This technique provides complete tunability of the filler particle parameters: shape, size (nanometer to micron), orientation, and composition. Both all-organic and polymer-ceramic composites have been generated using this technique, with particle inclusions ranging in size from 200 nm to 7 microns. The all-organic composites have been prepared with thermoplastic particle inclusions, such as polyvinylpyrrolidone, polystyrene, and the semi-conducting polymer, poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). Crosslinked particles, such as poly(trimethylolpropane ethoxylate triacrylate), were also incorporated into the composites. The particles were incorporated into crosslinked matrices, such as poly(ethylene glycol) (PEG), epoxy, and PFPE. Two examples of polymer-ceramic composites that have been fabricated with controlled microstructure are PFPE-barium titanate (PFPE-BaTiO3) and PFPE-cadmium oxide (PFPE-CdO). SEM, optical and confocal microscopy are used to image the composite films. Efforts are currently focused on the optimization of the fabrication process, and the characterization of the electrical and optical properties of the multilayered composite films.
9:00 PM - BB8.9
Regulating Thermosensitivity and Surface Properties of Poly(N-isopropylacrylamide) through Micropatterning.
Huijie Hou 1 , Yaping Hou 2 , Melissa Grunlan 2 , Arum Han 1
1 Electrical and Computer Engineering, Texas A&M University, College Station, Texas, United States, 2 Biomedical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractHydrogels that can respond to external stimulus have found various applications in biomedical research areas. Poly(N-isopropylacrylamide) (PNIPAAm) hydrogels exhibit a volume phase transition temperature (VPTT) of ~33 °C and so reversibly swell and deswell with changes in their temperature, therefore changing their surface properties from hydrophilic to hydrophobic and vice versa. To increase the responsiveness of hydrogels, methods such as decreasing the thickness of PNIPAAm layers, addition of surfactants, and various co-polymerization methods have been introduced. In this study, we created micropatterned PNIPAAm surfaces with arrays of PNIPAAm pillars (pillar diameters: 100 ~ 200 μm, edge to edge separations: 50 ~ 300 μm, height: 100 μm) to modify surface properties and thermoresponsiveness. Photopolymerization combined with a photolithography mask was used for simple fabrication of the micropillar array. Colloidal polysiloxane nanoparticles (200 nm diameter) were also incorporated to tailor the swelling behavior while maintaining the VPTT. Dynamic thermosensitivities of the pure and “nanocomposite” micropillars (210 μm and 120 μm in diameter) were measured while changing the temperature from room temperature (RT) to above VPTT, and then back to RT. Compared with 210 μm micropillars, 120 μm micropillars showed much higher swelling and deswelling rates (3.3 and 2.6 times difference respectively in the case of pure PNIPAAm micropillars, 3.3 and 2.0 times difference in the case of nanocomposite PNIPAAm micropillars). The 120 μm micropillars also shrunk more significantly compared to the 210 μm micropillars (35 % versus 73 % of their original sizes for pure PNIPAAn micropillars, 44 % and 62 % of their original sizes for nanocomposite PNIPAAm micropillars). These results demonstrate that the thermoresponsiveness of PNIPAAm is controllable by adjusting the size of the micropillars where increased responsiveness can be observed with decreasing micropillar diameters. Contact angle tuning of PNIPAAm surfaces was also demonstrated by changing the micropillar sizes, their separations, and compositions. By controlling those factors, contact angle of the surfaces could be changed from 9 ° to 123 °. Contact angles of the micropatterned surfaces increased with decreasing micropillar sizes, decreasing micropillar separations, and addition of polysiloxane nanoparticles into the gel. The developed method presented here can be used to dramatically change the thermoresponsiveness and surface properties of hydrogel surfaces by simply changing the size, distribution, and composition of hydrogel micropillar arrays using a simple fabrication step.