Symposium Organizers
Jaime Grunlan Texas A&M University
Sergei Nazarenko The University of Southern Mississippi
Jeff Bahr Nanocomposites, Inc.
Eliane Espuche University Claude Bernard Lyon 1
Symposium Support
Tyco Electronics, Schlumberger, 3M, Bayer
DD1: Electrically Conductive Nanocomposites
Session Chairs
Mark Ellsworth
Jaime Grunlan
Monday PM, November 28, 2011
Room 201 (Hynes)
9:00 AM - **DD1.1
Graphene-Elastomer Composites for Strain Sensing Application.
Jonathan Coleman 1 2
1 School of Physics, Trinity College Dublin, Dublin Ireland, 2 CRANN, Trinity College Dublin, Dublin Ireland
Show AbstractGraphite was exfoliated in Polyurethane (PU) solutions to give PU-stabilized, dispersed graphene. Freestanding composite films were fabricated by drop-casting. A range of films were made with graphene mass fraction varying from 0% to 90%. Measurement of DC conductivity shows percolative behaviour with percolation threshold, pc = 0.04 (8% weight) and percolation exponent of 3.7+-0.5. The conductivity reaches 126 S/m for high loading. The 90% film displayed a strain at break of 4%. This increased with decreasing graphene content to 500% for the 8% sample. These samples are ideal for use as strain sensors. To test this, films were subjected to tensile tests while the electrical resistance was monitored. Electro-mechanical tests shows a linear change in electrical resistance in the 0% - 25% strain range depending on the loading. The strain sensitivity (Gauge factor, GF=((R-R_0)/R_0 )/∈ ) was determined from the slope of linear region. The sensitivity for the film just above the percolation threshold was 7 and shows maxima for the film of mass fraction 18% having sensitivity 13. Above this the sensitivity starts decreasing with increased loading. These films shows higher sensitivity compare to conventional resistance-type strain gauges. We have extended this work to composites of PU filled with carbon nanotubes, silver nanowires and exfoliated flakes of NbSe2.
9:30 AM - **DD1.2
Electrical Percolation Behavior in Polymer Nanocomposites.
Rosario Gerhardt 1
1 , Georgia Institute of Technology, Atlanta , Georgia, United States
Show AbstractMuch has been said about how the size, shape and distribution of conducting fillers affects the percolation behavior in polymer nanocomposites. In spite of hundreds or even thousands of articles reporting on what controls whether a given polymer/conducting filler composite material system will percolate or not, many questions still remain. Part of the problem is that many of the research papers focus on a given system, using some specific fillers, that are mixed with insulating polymers by one preferred method or another. Thus, it is very difficult to make accurate comparisons between different research papers unless the materials used are identical and the methods used to fabricate the composites are similar or preferably identical. Some things are clear: (1) the larger the fraction of excluded volume, the lower the percolation threshold, (2) the smaller the size of the filler, the more likely it is that the percolation threshold will be low, (3) if the fillers are anisotropic, the properties will be different when the fillers are randomly oriented or if they show a preferred orientation, (4) the method by which the polymer/filler are mixed and the temperature at which the composite is consolidated tend to determine the resultant electrical properties. In this presentation, a summary of research conducted over the last ten years on a series of polymer composites made by various processing methods will be given and contrasted to results published in the literature.
10:00 AM - **DD1.3
Electrical and Thermal Aspects of Carbon Nanotube Nanocomposite Electrodes.
Brian Landi 1 , Matthew Ganter 1 , Chris Schauerman 1 , Paul Jarosz 1 , Cory Cress 2 , Ryne Raffaelle 3 , Reginald Rogers 1 , Jason Staub 1
1 , Rochester Institute of Technology, Rochester, New York, United States, 2 , US Naval Research Labs, Washington, District of Columbia, United States, 3 , NREL, Golden, Colorado, United States
Show AbstractThe use of carbon nanotubes (CNTs) as a conductive additive or free-standing support matrix in electrochemical device applications has several advantages compared to other carbon materials like carbon black, acetylene black, or even carbon fibers. CNTs have a high theoretical electrical conductivity and room temperature measurements exceed 1 x106 S/m for the doped-purified materials. The high aspect ratio of CNTs (ratio of length to diameter which is >10,000 for typical materials) compared to the other carbon materials allows for lower weight loading levels to achieve a comparable percolation threshold in a polymer composite. CNTs also have remarkable thermal conductivity properties that can promote effective heat dissipation within a composite, potentially enhancing the safety over composite electrodes with inferior carbon additives. In addition, the mechanical properties of CNTs exhibit both strength and flexibility: attractive features to prevent cracking during operation or in vibration environments. In the case of battery electrode nanocomposites, the ability to use CNTs as an additive or freestanding support shows tremendous promise to enable higher reversible capacities and rate capability while improving battery cyclability. Recently, the replacement of traditional conductive carbon additives with single wall carbon nanotubes (SWCNTs) in lithium metal oxide cathode composites has been shown to enhance thermal stability as well as power capability and electrode energy density. The dispersion of 1% w/w high purity laser-produced SWCNTs in a LiNi0.8Co0.2O2 electrode created an improved percolation network over an equivalent composite electrode using 4% w/w Super C65 carbon black; evidenced by additive connectivity in SEM images and an order of magnitude increase in electrode electrical conductivity. The cathode with 1% w/w SWCNT additives showed comparable active material capacity (185-188 mAh/g), at a low rate, and coulombic efficiency to the cathode composite with 4% w/w Super C65. At increased cycling rates, the cathode with SWCNT additives had higher capacity retention with more than three times the capacity at 10C. The thermal stability of the electrodes was evaluated by differential scanning calorimetry after charging to 4.3V. A 40% reduction of the cathode exothermic energy released was measured when using 1% w/w SWCNTs as the additive. Thus, the results demonstrate that replacing traditional conductive carbon additives with a lower weight loading of SWCNTs is a simple way to improve the thermal transport, safety, power, and energy characteristics of cathode composites for lithium ion batteries. A comparison of the varying CNT material properties as a function of synthesis, purification, and chemical processing on the electrical properties of nanocomposites will be provided. This will serve as a point to discuss the electrical and thermal implications of using CNTs for energy storage and transmission applications.
10:30 AM - DD1.4
Impedance Response and Modeling of Percolated-Composite Varistors Containing Aligned Semiconductor Whiskers: Effects of dc-Bias Partitioning, Sample Size, Composition, Filler Interfaces, and Tendencies of the Current Distribution in the Percolated Cluster.
Brian Bertram 1 2 , Rosario Gerhardt 1 , John Schultz 2
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2 Signature Technology Lab, Georgia Tech Research Institute , Atlanta , Georgia, United States
Show AbstractImpedance spectroscopy and modeling were used to investigate the partitioning of 0-40 V dc bias in composites of an insulating matrix material and variable volume fractions of semiconductor fillers, which formed low-connectivity percolated clusters. Specifically, the matrix was alumina and the fillers were silicon carbide whiskers, but the results and unique modeling approach may have fairly general applicability to other percolated insulator-(semi)conductor composite systems. Differences in response between long (~25 cm) composite rods and thin (~1.7 mm) slices thereof were interpreted in terms of the relative contributions to the impedance from the electrodes and SiCw-percolated clusters of the composite samples. Bias had minimal effect on the impedance of rods because its distribution across the long percolated clusters within translated to low electric fields at the filler-filler interfaces. The impedance of thin slices was more sensitive to bias and was mainly due to such interfaces. The associated dc resistance and effective capacitance decreased significantly with increasing dc bias. The capacitance trend indicated symmetrical Schottky energy barriers at the interfaces and outputted a characteristic parameter. Different models of the non-linear current-voltage behavior were related to each other and indicated weak varistor behavior, i.e. a varistor non-linearity coefficient between 1.15 and 2.57. With increasing filler content and composite dc conductivity, the characteristic capacitance parameter increased and the non-linearity strength decreased. Also, the exponent t describing conductivity divergence at percolation was reduced at large dc bias. An original model of the percolated clusters was developed and correctly predicted the qualitative character and some quantitative aspects of these experimental results. The model is based on tendencies of the current distribution which are expected from the topological structure and contrast between interface/intrafiller electrical behavior. Accordingly, it outputs the voltage-distribution tendencies.
10:45 AM - DD1: Conductive
BREAK
11:15 AM - DD1.5
Effect of Nanowire Size Dispersity on the Electrical Conductivity in Polymer Nanocomposites.
Rose Mutiso 1 , Michelle Sherrott 1 , Ju Li 1 , Karen Winey 1
1 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractIn this simulation study, we model the percolation threshold and electrical conductivity of three-dimensional networks containing finite, conductive cylinders with experimentally typical (Gaussian) and engineered (bidisperse) distributions in their length and/or diameter. We have previously used this approach to explore the effects of cylinder orientation and aspect ratio on the electrical properties [1, 2]. Our results show that narrow Gaussian distributions do not affect the threshold concentration or electrical conductivity significantly in both isotropic and oriented networks, while the addition of a small fraction of longer rods in a bidisperse system can improve the electrical properties considerably. A generalized analytical model for the percolation threshold of polydisperse rod networks was recently developed by Otten and van der Schoot using approaches from both percolation and liquid state theories [3]. However, their solution is only exact in the slender rod limit (L/D→ infinity). Studies by Berhan et al. [4] showed that convergence to the slender rod limit solution for percolation of rods is very slow and is not achieved even for aspect ratio values as high as L/D=500. Thus, the Otten and van der Schoot analytical solution has limited applicability to rod-like fillers with very high aspect ratio above typical experimental ranges. To this end, we have obtained a numerical calibration factor from our simulation data that extends their analytical model for percolation in polydisperse networks to networks of soft-core rods with finite-L/D. References:[1] White, S.; DiDonna, B.; Mu, M.; Lubensky, T.; Winey, K. Physical Review B. 2009, 79, 1-6.[2] White, S. I.; Mutiso, R. M.; Vora, P. M.; Jahnke, D.; Hsu, S.; Kikkawa, J. M.; Li, J.; Fischer, J. E.; Winey, K. I. Advanced Functional Materials. 2010, 20,2709-2716.[3] Otten, R. H.; van der Schoot, P. Physical Review Letters. 2009, 103, 1-4.[4] Berhan, L.; Sastry, A. Physical Review E. 2007, 75, 1-8.
11:30 AM - DD1.6
Graphene Polyimide Nanocomposites.
Mitra Yoonessi 1 2 , Matthew Dittler 2 , Daniel Scheiman 3 , Marisabel Lebron-Colon 2 , James Gaier 2
1 , Ohio Aerospace Institute, Cleveland, Ohio, United States, 2 , NASA Glenn Research Center, Cleveland, Ohio, United States, 3 , ASRC, Cleveland, Ohio, United States
Show AbstractHighly aromatic polyimide resins with high thermal stability (> 450 oC), high glass transition temperature (> 200 oC), high tensile strength, low creep, radiation shielding, flexibility, and low color are excellent for aeronautics and space structural components. Their properties can be improved by addition of nanoparticles such as carbon nanotube, silica, POSS, vapor grown carbon nanofiber, silver nanoparticles, and graphene. Graphene is sp2-bonded mono-atomic thick quasi two-dimensional nanoparticle consists of 6-membered carbon rings with micron-sized lateral dimension, first reported as free standing nanoparticles by Geim (1).Polyimide of bisphenol A dianhydride (BPADA) and 4,4’-Bis(4-aminophenoxy)biphenyl (BAPP) was prepared by polycondensation reaction. This polyimide possess high glass transition temperature (> 210 oC), high thermal stability (> 500 oC), and high modulus. Graphene in form of reduced, highly oxygenated, and surface modified with imide moieties were incorporated in the polyimide matrix to generate polyimide graphene nanocomposites. Surface modifications of highly oxygenated graphene with imide moieties were performed using step-by-step grafting from method. A rigid surface modifier of with 3,3',4,4'-Biphenyl tetracarboxylic dianhydride (s-BPDA) and 2,2'-Dimethyl-4,4'-diaminobiphenyl (m-Tolidine) and a flexible modifier of BPADA and BAPP were grafted to the graphene surface. Surface modifications of graphene by imide moieties were studied by FT-IR, TGA, and XPS. Graphene with rigid surface modifier exhibited excellent dispersion in NMP stable in extended period of time. Nanocomposites of reduced graphene polyimide (0.1-4 wt%) were prepared by solution mixing and sonication followed by solvent casting. These graphene polyimide nanocomposites exhibited high conductivity of ~ 0.9 S/cm at plateau level, and low percolation volume fraction. Nanocomposites of oxygenated graphene polyimide and surface modified graphene were prepared by in-situ polymerization. This method utilized dispersed graphene in NMP in the presence of monomers. Thermal and mechanical properties of these nanocomposites were examined by DMA and TGA. Transmission electron microscopy results showed well exfoliated graphene nanoparticles in the polyimide matrix.1)Novoselov, K. S.; Geim, A. K.; et. al Science 2004, 306, 666-669.
11:45 AM - DD1.7
Analysis of Electrical Percolation Thresholds in Nanostructure Based Polymer Composites.
Steve Pfeifer 1 , Prabhakar Bandaru 1
1 , UC, San Diego, la Jolla, California, United States
Show AbstractIt is of scientific and technological interest to analyze the minimal concentration of carbon nanotubes (CNTs) necessary to form a percolating network. From a practical perspective, CNT networks have been proposed as constituents of thin film transistors for electronics and biosensors, polymer composites for electromagnetic interference shielding, etc., While variability in device characteristics was considered, the widespread unpredictability in the intrinsic geometry, e.g., the length (L) of the CNTs, has not yet been modeled. Such issues with predictability of the geometry are typical of nanostructure synthesis processes and could strongly influence the electrical characteristics and device properties. The prediction of a threshold is also pertinent in the synthesis of CNT based composites, where the cost of the nanostructures is a major factor. We then suggest a method for the a priori determination of the electrical percolation threshold in carbon nanotube (CNT) networks, of relevance in electronic devices, polymer composites etc. The variability in the CNT lengths, commonly observed in practical processing and dispersion, was also considered and the resulting probability distribution function determined to be of the Weibull type. Subsequently, the predicted percolation threshold volume fractions for single-walled CNTs, ~ 0.00073, and multi-walled CNTs, ~ 0.0193, were found to be in close correspondence to the experimentally determined values of 0.0011 and 0.0147, respectively.
12:00 PM - **DD1.8
Conductive Composites: Applications and Advances.
Mark Ellsworth 1
1 Research and Development, TE Connectivity, Menlo Park, California, United States
Show AbstractConductive composites generally consist of an electrically conductive particulate dispersed in a polymer matrix. The electrical properties of these composite materials are varied across a broad spectrum of properties by the appropriate formulation parameters such as the composition, size, and shape of the conductive components; the properties of the base polymer; additives to the formulation; processing conditions, and the form factor in which the materials are ultimately used. Carbon filled conductive composites are particularly unique due to the variety of available forms of carbon. Current applications using carbon filled conductive composites include EMI/RFI shielding, self-limiting heater cables, high voltage cable accessories, and overcurrent protection devices. Recent advances in carbon nanotubes and graphene have resulted in materials with high electrical conductivity at low volume loading levels, and materials with high energy storage potential. We have focused our recent efforts on the properties and potential applications of graphene. In particular, we have developed a freeze-drying method for preparing porous graphene aerogels with a high degree of accessible surface area. These materials are showing promise in light weight conductive composites, and more recently in energy storage devices.
12:30 PM - DD1.9
Conductivity Enhancement and Electromechanical Properties of Electric Field Aligned Carbon Cone Wires.
Matti Knaapila 1 , Henrik Hoyer 1 , Gorm Johnsen 1 , Geir Helgesen 1 , Mark Buchanan 2 , Jakob Kjelstrup-Hansen 3
1 Physics Department, Institute for Energy Technology, Kjeller Norway, 2 , CondAlign AS, Kjeller Norway, 3 NanoSYD, University of Southern Denmark, Sønderborg Denmark
Show AbstractWe show how an alternating electric field (dielectrophoresis) can be used to assemble carbon nanocones (CNCs) and align these assemblies into microscopic wires in diverse polymer matrices. The wires form continuous pathways that may electrically connect the alignment electrodes which can be placed in-plane or out-of-plane. This leads to directional conductivity and conductivity enhancement of 3 orders of magnitude in the case where the CNC fraction (~0.2 vol-%) is 1 order of magnitude below the percolation threshold (~2 vol-%). The alignment and conductivity are maintained on curing that joins the alignment electrodes together. It is also possible to prepare single wires that are typically 0.5-3 micrometers thick and 10-100 micrometers long. The electrical properties of these wires are sensitive to small deformations.
12:45 PM - DD1.10
Dielectric Breakdown at Polymer/Oxide Interfaces.
Roger Diebold 1 2 , Michael Gordon 3 , David Clarke 2
1 Materials Department, University of California, Santa Barbara, Santa Barbara, California, United States, 2 Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 3 Chemical Engineering Department, University of California, Santa Barbara, Santa Barbara, California, United States
Show AbstractThe maximum achievable strain that can be produced by a dielectric elastomer actuator is largely determined by the dielectric breakdown strength of the elastomer. To design improved materials for actuation purposes, it is imperative to understand the fundamental mechanisms governing electrical breakdown in these systems.The materials of interest are filled silicone elastomers, typically polydimethylsiloxanes, which contain high volume fractions of fumed silica nanoparticles to enhance their strength and toughness. It is well known that as the filler particle diameter decreases to the nanometer length scale, the particulate surface area to volume ratio increases dramatically, consequently determining many of the physical properties of the macroscopic composite. Thus, the interface between the filler particle and the bulk polymer is critical to understand in terms of electronic transport.In this paper, the authors will present conductive atomic force microscopy results of electrical failure at idealized oxide/polymer interfaces which emulate those found in filled elastomer systems. Self assembled monolayers deposited on planar silica surfaces are used to modify the chemistry of the interface while minimizing morphological effects. Weibull and I-V curve analysis will be used to describe the effects of silane coupling agent functionalization on dielectric breakdown, and in particular, how different chemical moieties play a role in high-field interfacial electronic transport.
DD2: Multifunctional Nanocomposites (Antiflammable, Antireflective, etc.)
Session Chairs
Mickael Castro
Jean-Francois Feller
Monday PM, November 28, 2011
Room 201 (Hynes)
2:30 PM - **DD2.1
Thermal Degradation and Fire Retardance of Polymer Nanocomposites.
Giovanni Camino 1
1 Materials Science and Chemical Engineering, Polytechnic of Turin, Alessandria Italy
Show AbstractFlammability of polymers still represents a major limitation to their use and to the ensuing beneficial effect on industrial development. Indeed, flammability is related to fire risk (probability of fire occurrence) and hazard (consequences of a fire) in a number of applications of polymer materials such as in the electrical-electronic (E&E), transportation, building and furniture sectors. The concern about negative impact on environment and on health by well established, versatile and effective halogenated Fire Retardants (FRs) has driven the enforcement of new European regulations progressively restricting their use since the year 2000. Some halogenated compounds (e.g. penta- and octa-bromodiphenyl ether) are already banned, whereas some other FRs are currently undergoing a risk assessment procedure. To comply with regulations requests, new fire retardant strategies are being developed aiming at materials characterised by both low fire risk and hazard which simultaneously comply also with the modern environmental requirements globally defined as “sustainable development”. Most promising approaches involve polymer surface protection promoted by heat of the flame, thus reducing the rate of thermal degradation of the polymer, which supplies the fuel to the gas phase. In particular, a breakthrough could come from surface ceramisation and charring taking place in the combustion of polymer nanocomposites.Indeed, during combustion of nanocomposites, polymer ablation rapidly leads to the accumulation of a network of floccules on the surface, mainly made of nanoparticles, whatever their chemical composition and aspect ratio, combined with a relatively small fraction of carbonaceous char. Partial charring of burning polymer induced by the presence of nanofillers is a typical result of nanocomposites combustion, particularly evident in the case of polymer matrices which do not produce charred residue when burned by themselves.This thermally stable ceramic-char surface layer is able to act as a thermal shield by surface re-irradiation and as a barrier to heat and oxygen transfer from flame to the material and of degradation products from the material to the flame. Thus, the overall rate of flame feeding by combustible products from polymer pyrolysis and thermo-oxidation is decreased. Hence rate of combustion and of heat release are decreased accordingly.
3:00 PM - DD2.2
Use of Förster Resonance Energy Transfer (FRET) as a New Characterization Method for the Interface in Nanocomposites.
Jeffrey Gilman 1 , Mauro Zammarano 2 1 4 , Paul Maupin 3 , Li-Piin Sung 4 , Edward McCarthy 1 , Yeon Kim 4 , Douglas Fox 2
1 Polymers Division, Materials Measurement Laboratory, NIST, Gaithersburg, Maryland, United States, 2 Chemistry Department, American University, Washington, District of Columbia, United States, 4 Engineering Laboratory, NIST, Gaithersburg, Maryland, United States, 3 Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, US Department of Energy, Washington, District of Columbia, United States
Show AbstractFRET combined with laser scanning confocal microscopy, LSCM, can be used to monitor the amount and quality of interface formation at the nanoscale. FRET is a process by which a fluorophore (the donor), in an excited state, transfers its energy to a neighboring molecule (the acceptor) by non-radiative dipole-dipole interaction. The energy transfer efficiency between a donor and acceptor at a distance R decreases sharply with R: it is equal to 50 % for R=R0 (where R0 is the Förster distance) by definition. Typical values of R0 are between 2 nm and 6 nm, thus the FRET efficiency is typically negligible for R>10 nm. In a composite, where both the reinforcing phase and the matrix are fluorescently labeled, FRET occurs only at a distance of a few nm from the interface, revealing the interface itself. This implies that FRET can encode in optical microscopy images, nano-features (i.e., extent of interface formation), which are beyond the resolution limit of optical microscopy (Abbe limit). By combining optical microscopy techniques (e.g., LSCM) with FRET, one can probe an area that is large enough to be representative of the entire sample (macroscale) and still retain information at a smaller scale (nanoscale).
3:15 PM - DD2.3
Graphene Exfoliation via In Situ Radical Polymerization.
Ken-Hsuan Liao 1 , Christopher Macosko 1
1 Chemical Engineering & Materials Science, University of Minnesota TC, Minneapolis, Minnesota, United States
Show AbstractPoly-urethane-acrylate (PUA) was found to disperse thermally reduced graphene (TRG) better after in situ polymerization. The resulting nanocomposite gave an ultra-low percolated concentration between 0.1 wt% and 0.25 wt%. Urethane-acrylate oligomer (UAO) was synthesized and diluted by tripropyleneglycol diacrylate (TPGDA) to form flowable UAO/TPGDA mixture (UA). TRG was solvent-blended in UA to form TRG/UA solutions, with a percolatation concentration 0.5 wt%, as measured by rheology and electrical resistance. TRG/UA solutions were polymerized by free radical in-situ polymerization with azobisisobutyronitrile (AIBN) as the thermal initiator. Percolation concentrations of polymerized TRG/PUA nanocomposites ranged between 0.1 wt% and 0.25 wt%, as determined by surface resistance measurements and dynamic thermomechanical analysis (DMA). X-ray diffraction suggests that the reason for improved dispersion after polymerization is that TRG is not fully exfoliated and some non-exfoliated TRG can be intercalated by UA using solvent-blending, sonication, and exfoliation by in-situ polymerization. Differential scanning calorimetry (DSC) was used to monitor the polymerization of TRG/UA solutions and thermal properties of polymerized TRG/PUA nanocomposites. Polymerization heat, glass transition temperature, and polymerization temperature are independent of TRG loading, though polymerization temperature is c.a. 10 C lower in the absence of TRG. TEM images of a 0.25 wt% TRG/PUA nanocomposite revealed a homogeneous dispersion of TRG in PUA.
3:30 PM - **DD2.4
Multi-Functional Nanoparticle Coatings.
Michael Rubner 1
1 Materials Science, MIT, Cambridge, Massachusetts, United States
Show AbstractA wide range of materials including charged polymers and nanoparticles can be sequentially assembled onto surfaces from aqueous solutions to form conformal thin film coatings with properties that are tunable at the nanoscale. These multilayer thin film coatings can be constructed from polymers, polymer-nanoparticle combinations and all nanoparticle assemblies. By controlling simple processing conditions such as solution pH and ionic strength, thin films with dramatically different properties can be constructed from the same materials. Nanoparticle assemblies designed to contain spatially periodic nanoporous regions can be used to create broadband anti-reflection coatings, highly reflective structural color coatings and templates for capillary condensation of functional molecules. The mechanical robustness of these coatings can be significantly enhanced by chemical and/or hydrothermal treatments that either introduce chemical crosslinks or partially fuse the nanoparticles together. The ability to conformally coat nanochannels as deep as 20 microns with these constructs opens the door to functionalized membranes and novel separation schemes. Nanoscale control over film thickness and architecture has enabled the development of a variety of multi-functional coatings exhibiting anti-reflection, anti-fogging and self-cleaning capabilities. Examples of these varied functional coatings will be described as well as the science and engineering underlying their unique capabilities.
DD3: Nanocomposite Membranes and Barriers
Session Chairs
Jaime Grunlan
Sergei Nazarenko
Monday PM, November 28, 2011
Room 201 (Hynes)
4:00 PM - DD3.1
Layer-by-Layer Assembled Stimuli-Responsive Nanopore Membranes.
Younghyun Cho 1 2 3 , Jaehoon Lim 1 2 3 , Kookheon Char 1 2 3
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 2 The National Creative Research Initiative Center for Intelligent Hybrids, Seoul National University, Seoul Korea (the Republic of), 3 The WCU Program of Chemical Convergence for Energy & Environment, Seoul National University, Seoul Korea (the Republic of)
Show AbstractSmart materials that can change their properties and structures in response to external stimuli have recently received much attention owing to many potential applications in biosensors, drug delivery systems, actuation devices, and many others. Among various preparation methods to realize these goals, the layer-by-layer (LbL) assembly, based on polyelectrolytes leading to swellable multilayers, is a powerful method because it can be applied to any shape and size of substrates and, at the same time, the multilayer films assembled at specific conditions show strong swelling behavior that can be modulated in response to post-treatment conditions. Furthermore, a variety of functional materials such as nanoparticles, quantum dots, graphenes, and biomaterials can be easily incorporated within the thin films with nanoscale control. For molecular level filtrations, the pore size of membranes containing cylindrical pores should be less than tens of nanometers. However, it has been regarded as a challenging task to deposit polyelectrotytes homogeneously on the sidewalls of nanoporous membranes with sub-100 nm pore diameters based on the LbL deposition method due to the well-known entropic entrance barrier problem. In the present study, by introducing swellable poly(allylamine hydrochloride) (PAH) / poly(sulfonated styrene) (PSS) multilayers into nanoscaled pores with less than 100 nm in diameter, we could additionally reduce and control the pore diameter of anodic aluminum oxide (AAO) membranes by adjusting post-pH treatment, yielding smart ultrafiltration (UF) or nanofiltration (NF) membranes with various cutoffs realized in one membrane. Based on swellable nanopores in membranes, the translocation behavior of small spherical molecules as well as linear macromolecules through stimuli responsive membranes has been studied in detail.
4:15 PM - **DD3.2
Nanocomposite Membranes for Gas Separations.
Benny Freeman 1
1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractThis presentation focuses on fundamental characterization of polymer/inorganic nanostructured membrane materials for gas separation applications. Examples will be presented where incorporation of nanoscale particles into rigid polymers enhances both permeability and selectivity, for certain separations, based primarily on the disruption of the polymer chain packing by the nanoparticles (i.e., by altering diffusion selectivity of the polymer matrix). Additionally, the presentation will discuss the incorporation into polymers of nanoparticles with specific interactions with particular gases (e.g., CO2) as a route to increase permeability and selectivity by altering both diffusion selectivity and solubility selectivity.
4:45 PM - DD3.3
Influence of Clay Deposition Concentration on Nano Brick Wall Thin Film Properties.
Morgan Priolo 1 2 , Daniel Gamboa 2 , Kevin Holder 3 , Jaime Grunlan 1 2
1 Materials Science & Engineering, Texas A&M University, College Station, Texas, United States, 2 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 3 Chemistry, Texas A&M University, College Station, Texas, United States
Show AbstractThin films of montmorillonite clay and polyethylenimine (PEI) were produced by alternately dipping a substrate into dilute aqueous mixtures containing each ingredient. Clay concentration in the aqueous deposition suspension was altered to analyze its influence on gas barrier and mechanical properties. Films created with 20 bilayers of pH 10 PEI with 2.0 wt. % clay in suspension exhibited greater gas barrier behavior than identical films created using 0.05, 0.2 or 1.0 wt. % clay. After 24 clay-polymer layers were deposited onto 7-mil PET, the resulting transparent film exhibits an oxygen transmission rate below the detection limit of commercial instrumentation (< 0.005 cm^3/(m^2 day atm)). This level of oxygen barrier is believed to be due to a nano brick wall structure, revealed by transmission electron microscopy. With super gas barrier and optical transparency greater than 95%, this thin film is a good candidate for foil replacement in food and flexible electronics packaging.
5:00 PM - DD3.4
Expanding the Range of Nanocomposite Barrier Properties Measurement and Modeling.
Erik Dunkerley 1 , Daniel Schmidt 1
1 Plastics Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show AbstractPolymer nanocomposites based on layered nanofillers have received substantial attention from both academic and industrial researchers for over two decades. While these efforts have often focused on enhancing mechanical properties, it is telling that the commercial applications of polymer nanocomposites often take advantage of their barrier properties. Geometric tortuosity is typically invoked to explain such properties, and a number of models have been proposed to describe the properties of such systems.Much of the experimental work in this area has focused on nanocomposites containing relatively low concentrations of layered nanofillers. Historically, this has left significant gaps in the experimental data on nanocomposite barrier properties. More recently, the commercial application of high nanofiller content nanocomposite dispersions as well as academic research utilizing layer-by-layer deposition and papermaking techniques helped to fill in some of these gaps, but complete datasets from well-defined model systems spanning a wide range of compositions are still needed.In this work we introduce automated spray deposition as a novel method for preparing so-called “nanolaminates,” free-standing thin films containing arbitrary amounts of highly aligned clay nanoalyers, as a means of creating model systems ideal for exploring nanocomposite barrier properties. This approach is applied over a range of compositions, from pure polymer to pure (modified) nanofiller, for multiple base resins. The structure of these materials is assessed by scanning electron microscopy, while intercalation and orientation levels are quantified via two-dimensional x-ray diffraction.The oxygen permeability of these materials is then investigated and compared with the results from four of the most commonly used approaches to barrier modeling in such systems. Additionally, a general means of accounting for experimentally measured levels of layer orientation is developed, and the consequences of such corrections on model fit are presented. Finally, the envelopes of each orientation-corrected model are explored, and the effects of temperature are examined as well. Taken together, these results demonstrate a useful approach for the preparation of model systems for barrier modeling, and demonstrate the extent to which barrier properties improvements may be realized and modeled using tortuous path arguments as a function of composition and temperature.
5:15 PM - DD3.5
Transparent Nano Brick Wall Super Gas Barrier Polymer-Clay Assemblies.
Morgan Priolo 1 2 , Daniel Gamboa 2 , Kevin Holder 3 , Jaime Grunlan 1 2
1 Materials Science & Engineering, Texas A&M University, College Station, Texas, United States, 2 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 3 Chemistry, Texas A&M University, College Station, Texas, United States
Show AbstractThin films of sodium montmorillonite clay and weak polyelectrolytes were prepared by alternately exposing a PET substrate to four different dilute aqueous mixtures (polyethylenimine, poly(acrylic acid), polyethylenimine, and montmorillonite clay). After depositing four of these quadlayers (QL), the resulting transparent film exhibits an oxygen transmission rate below the detection limit of commercial instrumentation (< 0.005 cm^3/(m^2 day atm)). This level of oxygen barrier, unprecedented for a clay-filled polymer composite, is believed to be due to a nano brick wall microstructure comprised of completely exfoliated clay bricks in polymeric mortar and clay layer spacing on the order of tens of nanometers. This 4 QL film exhibits the lowest permeability ever reported (≤5 x 10^-22 cm^3 cm/(cm^2 s Pa)), has a thickness of only 51 nm and an optical transparency of 95%, making it a true foil replacement technology useful for flexible electronics and microwaveable food packaging.
5:30 PM - DD3.6
Thermal and Oxygen Transport Properties of Polymer Nanocomposites in the Context of Highly Transient Heating.
Stephen Bartolucci 1 , Jeffrey Warrender 1 , Nasir Uddin 2 , Marc Nyden 2 , Jeffrey Wiggins 3 , Jo Ann Ratto 4
1 , US Army ARDEC-Benet Laboratories, Watervliet, New York, United States, 2 Materials Flammability Group, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 3 School of Polymers and High Performance Materials, University of Southern Mississippi, Hattiesburg, Mississippi, United States, 4 Polymer Thin Film Center of Excellence, US Army Natick Soldier RDEC, Natick, Massachusetts, United States
Show AbstractPolymer nanocomposites have been studied extensively for improved flammability properties. However, some applications can subject these materials to highly transient heating with heating rates that are orders of magnitude higher than those that are traditionally used to characterize polymer nanocomposites. In our work, we have studied the effects of highly transient heating using pulsed laser heating on the degradation behavior of materials such as polypropylene-nanoclay and other polymer nanocomposite materials. In this talk, we will report on the thermal and mass transport properties of our polymer nanocomposites that are relevant to degradation behavior during heating and the effect that the nanospecies loading and type, such as nanoclay and carbon nanotubes, have on the transport properties. The thermal conductivity and oxygen permeability results will be discussed in the context of how these materials behave during exposure to highly transient heating.
5:45 PM - DD3.7
Effect of Polymer Microstructure on Barrier Properties in Polyamide/Clay Nanocomposites.
Matthew Bernasconi 2 , Saurabh Toshniwal 2 , Kunal Tulsyan 2 , Daniel Schmidt 2 , Emmanuelle Reynaud 1
2 Plastics Engineering, UMass Lowell, Lowell, Massachusetts, United States, 1 Mechanical Engineering, UMass Lowell, Lowell, Massachusetts, United States
Show AbstractAddition of nanofillers to polymer matrices gives enhanced barrier properties, but separating filler effects from changes in polymer microstructure is challenging. In order to isolate these effects, we have performed a comparative study of nanocomposites based on analogous semi-crystalline and amorphous polymers.Here we report on two families of nanocomposites, one based on semi-crystalline polyamide-12 (PA-12, Grilamid L20G) and the other based on an amorphous copolyamide-12 (CPA-12, Grilamid TR90), in combination with an organically modified montmorillonite nanofiller (Southern Clay Products Cloisite 30B). Nanocomposites containing up to 1 vol% inorganic were twin-screw extrusion compounded, then sheet-extruded to produce films suitable for tensile and barrier testing. The desired nanofiller concentrations were confirmed via thermogravimetric analysis (TGA), while x-ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrated partial exfoliation in both cases. XRD also revealed the existence of the gamma crystalline phase of the polymer in the PA-12 family, independent of nanofiller content, while differential scanning calorimetry (DSC) showed no change in the glass transition temperature of the CPA-12 as a function of nanofiller content. In contrast, the degree of crystallinity of the PA-12 nanocomposite sheets were much higher than the pure matrix (i.e. around 33% vs. 12%), likely related to a combination of processing parameters and nanofiller-induced nucleation. Both oxygen and water vapor barrier properties were measured. Consistent with geometric tortuosity arguments, the addition of nanoclay decreased oxygen permeability by a similar factor regardless of polymer microstructure. The effects of nanofiller on water vapor permeability are more complex. While the CPA-12 nanocomposite sheets showed continuous decreases in water vapor permeability with increasing nanofiller content, consistent with the observed reductions in oxygen permeability, the PA-12 nanocomposite sheets showed a minimum in water vapor permeability at intermediate nanofiller loadings followed by an increase at higher loadings. Since the degree of crystallinity is similar in all PA-12 nanocomposites, this observation implies that the size, shape, and/or perfection of the crystalline domains must play an important role in determining the water vapor permeability of these materials.In sum, this study sheds light on some of the key differences observed when nanofiller addition occurs alone vs. in tandem with changes in polymer microstructure. These differences are not accounted for by current barrier models, but clearly have an important role to play in controlling the barrier properties of polymer nanocomposites. Further experimental studies on similar systems are underway to confirm the generality of these results.
DD4: Poster Session: Transport Properties in Polymer Nanocomposites
Session Chairs
Jeff Bahr
Eliane Espuche
Jaime Grunlan
Sergei Nazarenko
Tuesday AM, November 29, 2011
Exhibition Hall C (Hynes)
9:00 PM - DD4.1
Thermal Transport properties of Melt-Shear Oriented iPP/Carbon Nanotube Thin Films.
Georgi Georgiev 1 2 , Gajinder Hoonjan 1 , Ananta Adhikari 1 , Germano Iannacchione 3 , Peggy Cebe 2
1 Natural Sicences, Assumption College, Worcester, Massachusetts, United States, 2 Physics and Astronomy, Tufts University, Medford, Massachusetts, United States, 3 Physics, Worcester Polytechnic Institute, Worcester, Massachusetts, United States
Show AbstractTransport properties of polymer nanocomposites become increasingly important for many applications. Thermal conductivity is especially important in applications like temperature sensing and packaging. We chose Isotactic Polypropylene (iPP) as one of the most widely used polymers and mixed it with different concentration of carbon nanotubes (CNTs): 0.01%, 0.1%, 1%, 2% and 5% CNTs. We oriented the thin film samples using melt-shear at 200°C and 1Hz in a Linkam microscope sharing hot stage. We measured that the nanocomposites crystallization kinetics is greatly increased and the iPP crystal forms are modified by the nanotubes. We further explore the effects of different compositions of the nanocomposites on the thermal transport properties of the as prepared thin anisotropic films in directions parallel and perpendicular to their orientation. To confirm anisotropy, the sheared samples were analyzed using polarized optical microscopy (POM) and Two Dimensional Microscopic Transmission Ellipsometry (2D-MTE). It showed that CNTs couple to the smectic phase of iPP, improve its order upon shearing and the crystals created after the formation of the oriented smectic phase are strongly aligned parallel to the direction of shearing. We detected a sudden increase of birefringence at 151°C upon cooling during shearing of the samples, higher than the iPP crystallization temperature, indicating liquid crystalline ordering. 2D-WAXS technique was used to measure the anisotropy indicating strong ordering of the crystals as a function of the CNTs concentration.
9:00 PM - DD4.10
Influence of Polymer Particle Size on the Percolation Threshold of Electrically Conductive Latex-Based Composites.
Gregory Moriarty 1 , Katherine Sun 1 , James Whittemore 2 , James Rawlins 2 , Jaime Grunlan 1
1 Department of Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 2 Polymers and High Performance Materials, University of Southern Mississippi, Hattiesbury, Mississippi, United States
Show AbstractMonodispersed copolymer emulsions, each with a different polymer particle size, were used to investigate the effect of particle size on the electrical and thermomechanical properties of carbon black (CB)-filled segregated network composites. These emulsions were synthesized with equal amounts of methyl methacrylate (MMA) and butyl acrylate (BA), with latex particle size ranging from 83 to 771 nm. The electrical percolation threshold was found to decrease from 2.7 to 1.1 vol% CB as the latex particle size was increased. Microstructural images reveal diminished latex coalescence, and improved CB segregation, with increasing latex particle size. The glass transition temperatures for all systems were relatively unaltered, with changing CB concentration, while the storage moduli all increased. Furthermore, all systems exhibited a similar maximum electrical conductivity plateau of 0.7 S*cm-1, albeit at lower concentration for larger latex particle size. This ability to tailor percolation threshold with latex particle size provides an important tool for manipulating electrical and mechanical properties of polymer nanocomposites.
9:00 PM - DD4.11
Effect of Filler Dispersion on Space Charge Behavior in XLPE Nano Composites for HVDC Cable Applications.
Tung Ha 1 , Yongho Park 1 , Ikhyun Ryu 1 , Hosouk Cho 1 , Yoonjin Kim 1 , Jinho Nam 1 , Gunjoo Lee 1
1 Polymer Research Group, Advanced R&D Center - LS Cable & System, Anyang, Gyonggi, Korea (the Republic of)
Show AbstractRecently, polymeric nano-composite materials have been received much attention as a new insulation material because the properties of the original material can be dramatically improved by adding a small portion of nano-sized filler. Cross-linked Polyethylene (XLPE) was one of the most important insulation materials in power transmission cable and has been used widely for alternating current (AC) cables. However, under high DC electric field, a phenomenon called space charge accumulation happens within the polymeric material and greatly affects to the failure of DC cable. In order to prevent the packet charge, many researchers have been using nanoparticles as fillers in XLPE-based composites. The filler particles dispersed in polymeric phase act as trapping sites restraining the propagation of packet-like charge throughout the insulating layer, and therefore, preventing the accumulation of space charge. Obviously, dispersion of fillers in polymer matrix is the key factor to the success in the development of DC polymeric cable. In this report, we investigated the effect of filler dispersion on space charge behavior in XLPE nano composites. Before compounding, nano-sized MgO powders used as fillers in our experiments were subjected to surface treatment with different conditions and the effect of the treatment was estimated by measuring the wettability of treated powders in water by Washburn method. The dispersion of MgO in the composites was characterized by SEM- BSE (Back Scatter Electron) mode. Composites were subjected to hot-pressing into films as thin as 100μm, and space charge behavior was observed by a technique called Pulsed Electro Acoustic (PEA) under high DC electric fields (e.g. 80kV/mm, 100kV/mm and 150kV/mm). Calculated charge quantity and maximum generated electric field within the nano-composites will be discussed in detail. The main results showed that, the reduction of generated space charge was greatly dependent on the dispersion of MgO nano particles.
9:00 PM - DD4.12
Enzyme Integrated Nanostructured Redox Polymers for Biofuel Energy.
Joungphil Lee 1 , Ilyoung Choi 2 , Hyungmin Ahn 1 , Moon Jeong Park 1 2
1 Chemistry, Postech, Pohang Korea (the Republic of), 2 Division of Advanced Materials Science, Postech, Pohang Korea (the Republic of)
Show AbstractThere are growing needs to develop future energy source and concomitantly, extensive efforts have been paid to a variety of systems such as fuel cells and batteries. For bio-micro system, enzymatic biofuel cells are particularly promising candidates where the electrical current can be produced with the use of biomass, i.e., glucose, present in the human body. However, limitations in the operation of common biofuel cells are connected with inefficient fuel transport to the active centers of enzymes and low electron transport rate between enzyme and electrode surface, which results in low power density. To solve this low power density problem, most widely used approach is the use of electron mediator such as carbon nanotubes and ferrocene derivatives for efficient electron transfer between enzyme and substrate. In present study, we have described a new approach, that of encapsulating enzymes by nanostructured redox polymers. Various polyferrocenylsilane (PFS) containing block copolymers have been employed as electron mediator, which can form different nanoscale morphology, i.e., bicontinous, wires, and nanoparticles, by varying molecular weights of copolymers and solvent compositions. The electrode is fabricated by layer-by-layer deposition of porous carbon, enzyme, and nanostructured PFS polymers. The stability of the enzyme integrated electrode is found to be improved by exposing the sample to osmium tetroxide vapor where dienes in polymers are selectively cross-linked. We have demonstrated that the electron transfer rate between PFS nanoobjects and enzyme is sensitive function of the morphology of PFS containing redox polymers. In particular, the utilization of bicontinous structures forming mediator results in remarkably enhanced current densities as well as good sensitivities at low glucose concentrations.
9:00 PM - DD4.13
Thermally Insulating and Transparent Glasses Based on Organosilicate Films Containing Hollow Silica Shells.
Heeje Woo 1 , Kookheon Char 1
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of)
Show AbstractHollow silica shells (HSSs) are attractive candidates as insulating materials due to their unique properties such as hollow inner space, porous shell structure, large surface area, low thermal & electrical conductivity, and high thermal stability. In the present study, we applied the basic principles of HSSs to thermally insulating glasses with high transparency. The HSSs were prepared using poly(acrylic acid) (PAA) colloidal aggregates as templates, tetraethyl orthosilicate (TEOS) as a silica precursor, and ammonia hydroxide as a catalyst based on the modified Stöber method. PAA dissolved in aqueous ammonia hydroxide was first mixed with ethanol, a poor solvent, to form PAA colloidal aggregates and TEOS was then added to the mixture to form silica shells on the surfaces of PAA colloidal aggregates. The prepared PAA@silica core/shell nanoparticles were washed with distilled water to remove the PAA templates, leaving behind HSSs. The average diameter of HSSs could be controlled from 30 to 100 nm with reasonable size uniformity. The organosilicate matrices were prepared by the sol-gel reactions with TEOS, methyltrimethoxysilane (MTMS), and 1, 2-bis (trimethoxysilyl)ethane (BTMSE) as monomers and hydrochloric acid as a catalyst. The HSSs mixed with organosilicate matrices were deposited on glass substrates to realize thermally insulating layers. The HSS-coated glasses show improved heat-blocking ability with high transparency.
9:00 PM - DD4.14
Gas Permeability and Mechanical Properties of PDMS Mixed with PMPS Nanofibers Produced by Electrospinning.
Atsushi Nakano 1 , Norihisa Miki 1 , Atsushi Hotta 1
1 Graduate School of Science and Technology, Keio University, Yokohama, Kanagawa, Japan
Show AbstractPolymethylphenylsilicone (PMPS) was electrospun to form a nanofiber sheet which was then blended with non-woven polydimethylsiloxane (PDMS) to produce a new type of polysiloxane composite. The microstructure, the gas permeability and the mechanical properties of the PMPS/PDMS composite were investigated. PMPS, a siloxane polymer with a phenyl group, was successfully electrospun to fabricate silicone-nanofibers, where such types of siloxane nanofibers had not been reported so far. The electrospinning procedures were carefully examined and the spinning conditions were optimized by controlling polymer concentrations, electrospinning voltages, and several solvent characteristics. 21 solvents with different chemical properties (boiling point, conductivity, viscosity, dielectric constant and solubility parameter) were examined to fabricate different diameters of fibers ranging from 750 nm to 10 μm. PMPS was then mixed with PDMS by retaining the original nanofiber structures to produce a new type of nano-fibrous composite. The microstructure of the composite was studied by SEM, while the mechanical properties were examined by tensile tester, following the gas permeability testing.From the SEM measurements, it was found that the average diameter of the optimized PMPS nanofibers was ~750 nm. The surface area of PMPS fibrous structures was 800 times larger than that of an ordinary PMPS film surface. The gas permeability test revealed that the PMPS/PDMS composite presented higher CO2 permeability and higher CO2/N2 selectivity than the homogenous PDMS membrane. Moreover, CO2 permeability and CO2/N2 selectivity gradually increased by raising PMPS-fiber compounding ratio in the PMPS/PDMS composite. The mechanical properties of PMPS/PDMS composite showed higher Young's modulus and higher tension strength than pure PDMS. The mechanism of the enhancement of CO2 permeability, CO2/N2 selectivity, and the mechanical properties was discussed from the viewpoint of nano-interface between PMPS and PDMS along with the nanofiber network structures.
9:00 PM - DD4.16
Interaction and Electronic Structure of Polythiophene and Silicon Nanocrystals for Hybrid Polymer Composites.
Alexandra Carvalho 1 , Jose Coutinho 1 , Sven Oberg 2 , Mark Rayson 2 , Patrick Briddon 3
1 I3N, University of Aveiro, Aveiro Portugal, 2 Department of Mathematics and Engineering, Luleå University of Technology, Luleå Sweden, 3 School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne, Newcastle United Kingdom
Show AbstractSilicon nanocrystals (Si-NCs) and the organic polymer poly(3-hexylthiophene) (P3HT) composites have been used as the functional material for hybrid solar cells, where the silicon nanocrystals are used as electron acceptors and the polymer as a hole conductor [Liu et al.,Nano Lett., 2009, 9, pp 449]. Since the exciton dissociation takes place at the nanocrystal-polymer interface, there is great interest in understanding the adsorption geometry and its influence on the interfacial electronic structure. We have investigated the electronic structure of dodecathiophene (12T), a model compund for polythiophene, physisorbed on spherical, hydrogenated silicon nanocrystals. The preferred adsorption geometry corresponds to the parallel orientation of the thiophene rings relative to the surface. For Si-NCs with a diameter of about 2 nm , the semiconductor highest occupied and lowest unoccupied one-electron levels straddle the 12T gap, with an offset of about 1 eV between the highest occupied levels of both materials. Reducing the distance separating the 12T chain from the Si-NC, the levels of 12T shift downwards. We discuss how the chemical modification of the nanocrystal surface can be used to modify the level offsets.
9:00 PM - DD4.17
Bio-Inspired Layer by Layer PVA/GO and PVA/Reduced GO Nanocomposites.
Charline Sellam 1 , Zhi Zhai 1 , Hua Deng 3 , Emiliano Bilotti 1 , Ton Peijs 1 2
1 School of Engineering and Materials Science, Queen Mary University of London, London United Kingdom, 3 College of Polymer Science and Engineering, Sichuan University, Chengdu China, 2 Eidhoven Polymer Laboratories, Eindhoven University of Technology, Eindhoven Netherlands
Show AbstractBio-composites such as bones, teeth, or nacre are composed of mineral particles and a protein matrix with a superior strength and toughness. For example, nacre is 3000 times tougher than the mineral particles. Common features in bio-composites are there complex architectures with several orders of structure, different structures at different scales, arrangements and orientations, high volume fraction of particles and the smallest building block is at the nanoscale. Layer by layer (LbL) is a bottom-up approach leading to a highly hierarchical structured nanocomposite. The most well-known process used is dip coating which consists in dipping repeatedly a substrate into three solutions (polymer, filler, and aqueous media). A recent method based on freeze cast dried nanocomposites also leads to highly ordered 3D structure. Spraying is a recent, simple, versatile and rapid method for multilayer assemblies. It is a bottom-up approach, which consists in alternatively spraying two solutions (polymer & filler) on various substrates. The main advantage of spraying, besides being a rapid method, is the ability to grow a layer on any surfaces or 3D objects. Two dimensional particles such as graphene or graphene oxide are very attractive and promising for multifunctional nanocomposites and can out-perform 1D fillers. For mechanical properties, 2D particles have specific advantages over 1D particles because of the larger surface area in contact with the polymer matrix. The ability of Graphene oxide (GO) to disperse in aqueous solution as well as its ability to form H-bonding with polar polymers makes it a great candidate for spraying layer-by-layer composites.In this study, we present a layer by layer nanocomposites obtained by sequential deposition of PVA and GO in solution followed by chemical reduction. A uniform thin film consisting of 150 bi-layers is rapidly obtained over a large area. Each layer is characterised by AFM, and ellipsometry. The uniform growth is monitored by UV-Vis and the mechanical properties as well as the electrical conductivity of the composites are addressed in function of the orientation but also in function of the lamellar structure of the composites.
9:00 PM - DD4.18
Fabrication and Characteristics of Organic Thin Film Transistors with High-K Insulator of Polymer Nanocomposite.
Young-Jae Kim 1 , Joohee Kim 2 , Joohyun Lim 1 , Youn Sang Kim 2 , Jin-Kyu Lee 1
1 Chemistry, Seoul National University, Seoul Korea (the Republic of), 2 Nano Science & Technology, Seoul National University, Seoul Korea (the Republic of)
Show AbstractOrganic thin film transistors (OTFTs) have many advantages, such as light weight, flexibility, low cost of fabrication, and solution processability. However, traditional OTFTs often suffer from high operating voltage due to low the dielectric constant of organic materials (polymer). We fabricated low-voltage OTFTs incorporated with high dielectric nanoparticles in the dielectrics. The dielectric insulator consists of polymer and high K-nanoparticles such as TiO2. We enhanced the interaction between nanoparticles and polymer matrices by modifying the surface of nanoparticles with a ligand that has a structure similar to that of polymer repeating units. We suggest that addition of nanoparticles can promote significant change in dielectric constant because nanoparticles have a relatively high dielectric constant compare to polymer. The use of nanocomposite insulator with high dielectric constant might be expected to enable device operation at low voltage.
9:00 PM - DD4.19
Application of Spray Layer-by-Layer Assembled Composite Polyelectrolyte-Clay Thin Films as Selective Layers in Reverse Osmosis (RO) Membranes.
Jason Kovacs 1 , Paula Hammond 1
1 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractEfficient and economical water desalination can ameliorate humanity’s growing demand for freshwater from a diverse array of sources including seawater and industrial wastewater. Development of novel, highly-selective membranes for use in continuous reverse osmosis (RO) processes could greatly reduce both the capital and operating costs for modern desalination operations. The flexibility of the layer-by-layer (LbL) assembly process enables the deposition of composite polyelectrolyte/clay multilayer films on porous hydrophilic substrates to serve as selective layers. Assembly of multilayer films via the spray-LbL technique is particularly suited for the creation of selective layers because large asymmetric films can be deposited one to two orders of magnitude more quickly than with traditional dip-LbL assembly. The composition of spray-LbL assembled composite films can be fine-tuned by manipulating the assembly conditions; by adjusting the spray time for both the polyelectrolyte and the clay, it is possible to achieve film compositions between approximately 24% and 84% by weight of clay. Using irreversible thermodynamics to model RO membrane transport, permeability coefficients for water and salt through selective layers of varying film composition are calculated from trial runs in dead-end and cross-flow permeation cells. Preliminary data have confirmed the viability of using composite polyelectrolyte-clay platelet films to increase the selectivity of commercially available RO membranes.
9:00 PM - DD4.2
Optical Transport Properties of Oriented iPP/Carbon Nanotube Nanocomposite Thin Films.
Georgi Georgiev 1 2 , Gajinder Hoonjan 1 , Ananta Adhikari 1 , Germano Iannacchione 3 , Peggy Cebe 2
1 Natural Sciences, Assumption College, Worcester, Massachusetts, United States, 2 Physics and Astronomy, Tufts University, Medford , Massachusetts, United States, 3 Physics, Worcester Polytechnic Institute, Worcester, Massachusetts, United States
Show AbstractOptical Transport through Isotactic Polypropylene (iPP) and carbon nanotubes (CNTs) nanocomposite thin films is important to many applications where optical transmission or polarization are used. Especially interesting is the case where the optical properties are anisotropic as in oriented thin films and the optical transport is different in the direction of orientation and perpendicular to it. Changing the orientation of the film or the polarization of the light can change the way in which the nanocomposite film interacts with light. Our polymer of choice, Isotactic Polypropylene, is one of the most widely used polymers which will increase the applicability of our results. We blended iPP with different concentration of carbon nanotubes (CNTs): 0.01%, 0.1%, 1%, 2% and 5% and oriented the thin film samples using melt-shear at 200°C and 1Hz in a Linkam microscope sharing hot stage. We measured that the nanocomposites crystallization kinetics is greatly increased and the iPP crystal forms are modified by the nanotubes. To confirm anisotropy, the sheared samples were analyzed using polarized optical microscopy (POM) and Two Dimensional Microscopic Transmission Ellipsometry (2D-MTE). It showed that CNTs couple to the smectic phase of iPP, improve its order upon shearing and the crystals created after the formation of the oriented smectic phase are strongly aligned parallel to the direction of shearing. We detected a sudden increase of birefringence at 151°C upon cooling during shearing of the samples, higher than the iPP crystallization temperature, indicating liquid crystalline ordering. 2D-WAXS technique was used to measure the anisotropy indicating strong ordering of the crystals as a function of the CNTs concentration. Light scattering patterns are also altered by aligning the nanocomposite films uniaxially.
9:00 PM - DD4.20
Elaboration and Electrical Properties of Polymer-Multiwall Carbon Nanotubes Nano-Composite.
Tewfik Souier 1 , Guang Li 1 , Karim GadElrab 1 , Sergio Santos 1 , Matteo Chiesa 1
1 LENS : Material Science and Engineering, Masdar institue of Science and Technology, Abu Dhabi United Arab Emirates
Show AbstractMulti-Walled Carbon Nanotubes can be aligned directly during their synthesis, forming carpets and thus 1D anisotropic networks. The Aligned MWNTs can be impregnated in a polymer matrix, forming a 1D nanocomposite. The macroscopic electrical conductivity in the 1D direction is found to be higher in comparison to conductivities measured on randomly oriented CNT composites. In this context, our motivation is to study the electrical properties of 1D composite material at the nanoscale taking into account the fabrication parameters. Briefly, the MWNT carpets are synthesized by an aerosol-assisted CCVD on quartz substrates; they are annealed at 2000°C under argon atmosphere; and then they are impregnated in an epoxy polymer matrix and cured. The thickness of the composite is adjusted by polishing. The MWNTS are characterized, at each step of the fabrication process, by SEM and TEM. Typically, CNT’s are 1mm length with 50 nm in diameter. Their average density is about 10^9 MWNT/cm2.The interface of the composite is characterized by means of AFM with a sharp platinum conductive tip. The current sensing module (ORCA) allows a simultaneous mapping of the topography and of the local resistivity with a resolution of 4 nm. The average diameter and the density of CNT’s, in the current maps, are similar to the ones obtained by both SEM and TEM. Moreover, a low resistance of 10 kOhms has been measured in several areas of the surface confirming the high macroscopic electrical conductivity. Furthermore, I-V spectra are acquired on top of several CNT’s: linear curves characteristic of ohmic transport, and non-ohmic curves characteristic of either semiconducting character or coulomb blockade phenomena. Indeed, conductivity measurements on the same material at low temperature confirm the coulomb blockade phenomena. Complementary AFM measurements are currently in progress in order to explain and model the non-ohmic behaviour at room temperature.
9:00 PM - DD4.21
Oriented Polystyrene/SWNT Electrospun Nanofibers: Morphology, Thermal Properties and Electrical Properties.
Bin Mao 1 , Qian Ma 1 , Peggy Cebe 1
1 Physics and Astronomy, Tufts University, Medford, Massachusetts, United States
Show AbstractWell-aligned atactic polystyrene (PS) composite nanofibers with single wall carbon nanotubes (SWCNTs) were prepared using electrospinning onto a rotating drum collector. Scanning electron microscopy and transmission electron microscopy are used to characterize the fiber morphology (diameter, surface quality, uniformity and the size distribution) and the dispersion of SWCNTs inside the as-spun fibers respectively. Polymer chain orientation is verified from SAXS. Differential Scanning Calorimetry results show the decreasing in heat capacity step at Tg when carbon nanotubes are added, which indicates the formation of rigid amorphous near carbon nanotube surface. The electrical conductivities of aligned fibers are under investigation.
9:00 PM - DD4.22
Towards Homogenous Active Composites of Nanostructured Conducting Polymers in UV-Curing Polymeric Matrix.
Shadi Jafarzadeh 1 , Jinshan Pan 1 , Per Claesson 1 2
1 Chemistry; Surface and Corrosion Science, Royal Institute of Technology (KTH), Stockholm Sweden, 2 , Institute for Surface Chemistry (YKI), Stockholm Sweden
Show AbstractConducting polymers (CPs) are widely used as responsive materials that exhibit reversible changes in properties like oxidation state (REDOX), electrical conductivity, volume and color while exposed to specific environment. For many applications, making blends of CPs in a host polymeric matrix is a promising approach to overcome the poor processability and solubility of these materials. This work is focused on preparation of homogenous conductive composites of nanostructured polyaniline (PANI) and polyester acrylate (PEA), and one of the end usages is in smart coatings to provide self-healing systems with active corrosion protection on metal substrates. We discuss how the morphology and size of CP particles as well as compatibility within the multi-component system may influence dispersion homogeneity.PANI particles with a size smaller than 70nm were synthesized by the rapid mixing method and doped with phosphoric acid to achieve a good conductivity. Surface tension and contact angle measurements revealed a large Lewis base component for the PANI particles, suggesting preferential affinity towards liquids with some Lewis acid surface energy component. Indeed, slightly negative interfacial energies between PANI and PEA were found which suggested good compatibility of the two components and repulsion between PANI particles in the matrix. This is promising since small particle sizes favor high dispersion homogeneity and low percolation threshold, as a connected network is needed to keep all CPs active in the system. Smaller particles would also eliminate local mechanical defects as the expansion/shrinkage of the CP particles upon changes in the oxidation state would be more dominant in case of aggregation.PANI/PEA blends of different PANI content were prepared and optimized considering the above-mentioned studies. The UV sensitivity of composites and kinetics of the free radical polymerization were studied by Real-Time IR spectroscopy, with IR spectra continuously collected in situ under the UV lamp until full-curing. Here, the highest allowable PANI concentration without affecting the UV curing process was found and compared with theoretical calculations. UV-cured composite coatings of 10μm thickness were prepared, and the electrical bulk conductivity was measured by impedance spectroscopy. Moreover, the connectivity and distribution of the PANI particles in the cured films were followed by conductive atomic force microscopy (AFM-TUNA) combined with surface nano-mechanical properties mapping (Peak Force QNM). This is a powerful tool to find any correlation between conductive areas (assigned to current passing through the polymer matrix) with variations in material properties like modulus and deformation on the surface.Optimization of the CP particles distribution in polymeric matrix and study of the system in both liquid and crosslinked state made it possible to provide active electrically conductive composites of homogenous functionality.
9:00 PM - DD4.23
Effect of Annealing Temperature on High Thermal Conductivity Silver/Polymer Nanocomposites.
Fengyuan Lai 2 , Kamyar Pashayi 1 , Hafez Fard 1 , Theodorian Borca-Tasciuc 1 , Plawsky Joel 3
2 Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 1 Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractMetal polymer nanocomposites are of great interest as thermal interface materials to help spread and dissipate the heat generated from electronic devices. The thermal conductivity k of polymer nanocomposites is typically less than 10 Wm-1K-1, even when high k nanofillers are employed, due to the thermal interface resistance between nanoparticles and the polymer matrix or the absence of high k pathways. We recently demonstrated high k in bulk nanocomposites of silver nanoparticles dispersed in epoxy and cured at a relatively low temperature (150 °C). A nanocomposite with 30 vol % of 20nm nanoparticles exhibited k~30 Wm-1K-1. The mechanism responsible for enhancing k was found to be the self-assembly, through in-situ sintering, of high aspect ratio metallic networks inside the nanocomposites. We found that the nanoparticle sizes, nanoparticle loadings, polymer species and annealing temperatures played important roles in the formation of the metallic networks. In order to control and optimize the network structure and subsequently increase k even further, this work mainly focuses on studying the effect of annealing temperature on the structure of the nanocomposite. Detailed structural characterization of these nanocomposites is carried out by transmission electron microscopy (TEM). The influence of polymer species on the nanocomposites is also studied.
9:00 PM - DD4.24
Improving the Figure of Merit of Carbon Nanotube/Polymer Composite Thermoelectrics and an Analysis of Their Practical Application.
Corey Hewitt 1 , David Carroll 1 , Alan Kaiser 2 , Siegmar Roth 3 , Richard Czerw 4 , Matt Craps 4
1 , Wake Forest University, Winston Salem, North Carolina, United States, 2 , Victoria University of Wellington, Wellington New Zealand, 3 , Korea University, Seoul Korea (the Republic of), 4 , NanoTech Labs, Inc., Yadkinville, North Carolina, United States
Show AbstractCarbon nanotube/polymer composite thin films for use as thermoelectrics has become of interest recently due to their favorable properties. The combined high electrical conductivity of the nanotubes and low thermal conductivity of the polymer, along with Seebeck coefficients reaching 40 μV/K, lead to an improved figure of merit (ZT) over that of either material individually. This is due to the ability to slightly decouple the relationship between the thermoelectric parameters because of the heterogeneous structure. Single film ZT values reach 0.005, while the current best thermoelectrics, including bismuth telluride (Bi2Te3), have ZT values of 1. To increase the composite ZT, a conducting polymer such as polyaniline can be incorporated into the film. A 20% loading of polyaniline by weight is shown to increase ZT by 20% over the nonconducting polymer based composite. However, based on ZT alone, carbon nanotube/polymer thermoelectrics do not compete with Bi2Te3, but there are practical parameters not considered in calculating ZT, including production complexity, materials cost, and physical characteristics. These parameters are analyzed for both Bi2Te3 and carbon nanotube/polymer composites to determine what benefits they have over Bi2Te3. Based on this analysis, carbon nanotube/polymer composites have favorable production and structural properties over Bi2Te3 including ease of production and potentially lower cost if they are mass produced, and a light weight, flexible, and durable physical structure that could result in the use of these thermoelectrics in applications previously unrealized due to physical restraints. These single films can be combined and layered into multilayered thin film thermoelectric devices called Z-modules by using an alternating p-type/n-type layering structure. The thermoelectric voltage output is then proportional to the number of layers in the module, and is limited only by the heat source available. These Z-modules can be coupled together in a number of geometries to create an array of modules that can meet the specified power demands of the application.
9:00 PM - DD4.25
Resistive Switching in Single-Gap Metal-Nanowire Devices.
Rose Mutiso 1 , Karen Winey 1
1 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractTraditionally, bulk nanocomposites of electrically conducting particles and insulating polymers have been categorized as either insulating or conducting when the nanoparticle concentration is below or above the percolation threshold, respectively. In our recently published work [1, 2], we presented the first examples of reversible resistive switching in bulk, glassy polymer nanocomposites. At compositions close to the electrical percolation threshold, silver nanowire-polystyrene nanocomposites demonstrate reversible resistive switching upon increase voltage at room temperature. We proposed that resistive switching in these materials is the result of the field-induced formation of silver filaments that bridge adjacent nanowire clusters, extending the percolation network and decreasing the sample's bulk resistivity. This hypothesis is further supported by our temperature-dependent characterization of resistive switching in these nanocomposites between 10 and 300K. In order to further understand the resistive switching mechanism in our nanocomposites, we have designed single-gap nanowire devices comprised of metal strips separated by polymer-filled nanogaps ranging between 10nm to 100nm. Using these devices, the complexity of the bulk device is significantly reduced as the switching mechanism between a single polymer-mediated metal-nanowire junction is isolated. We have successfully fabricated these single-gap devices using electron beam lithography and preliminary results from our electrical characterization experiments are promising. We intend to study a variety of metal/polymer combinations in order to systematically study the effects of the metal work function, dielectric constant of the host and solubility of the metal in the polymer host on the resistive switching behavior. References: [1] White, S. I.; Vora, P. M.; Kikkawa, J. M.; Fischer, J. E.; Winey, K. I. Advanced Functional Materials. 2011, 21,233-240.[2] White, S. I.; Vora, P. M.; Kikkawa, J. M.; Fischer, J. E.; Winey, K. I. Journal of Physical Chemistry C. 2010, 114, 22106–22112.
9:00 PM - DD4.26
Encapsulated-PET/Nanosilver-Epoxy Phase Change Material Composites.
Kamyar Pashayi 1 , Hafez Fard 1 , Fengyuan Lai 2 , Joel Plawsky 3 , Theodorian Borca-Tasciuc 1
1 Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 3 Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractHigh heat capacity high thermal conductivity k materials are critical for thermal energy storage applications. We recently demonstrated high k in bulk nanocomposites of silver nanoparticles dispersed in epoxy and cured at low temperature (150C). A nanocomposite with 30 vol. % 20nm particles exhibited k~30 Wm-1K-1. The process responsible for enhancing k was found to be the self-construction, through in-situ sintering, of high aspect ratio metallic networks inside the nanocomposite. Polyethylene terephthalate (PET) is a thermoplastic polymer with high heat capacity and high curing temperature (~250C) which is an appropriate candidate as a PCM for thermal energy storage applications. In this work we investigate encapsulated phase change material/nanocomposite (PCMNC) engineered from PET as PCM in core, silver nanoparticles as thermal conductivity enhancer and epoxy matrix as a shell. We will present experimentally studies of the effect of the molar ratio of PET/epoxy and nanoparticle vol% on heat capacity and thermal conductivity of the composite.
9:00 PM - DD4.27
Synthesis and Thermal Properties of Au-Nanowire Network-Filled Polymer Composites for Heat Management in Nanodevice Packaging.
Nikhil Balachander 1 , Rutvik Mehta 1 , Linda Schadler 1 , Theo Borca-Tasciuc 2 , Ganpati Ramanath 1
1 Materials Science & Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractWe report the synthesis of a polymer composite filled with a metal nanowire network and investigate its thermal properties for exploring the use of the composite for heat management applications in nanoelectronics packaging. While polymeric composites filled with nanoparticles and carbon nanotubes have been widely studied, the use of high-aspect ratio metal nanostructures and their assemblies is new. We expect the interconnected mesh of metal nanowires to be more effective thermal channels due to inherent continuity, connectivity that can lead to percolation at lower filler loadings. Gold was chosen due to its high bulk thermal conductivity, high corrosion resistance, ease of nanostructure synthesis and its relatively low stiffness conducive for conformability at rough surfaces and interfaces. Sub-gram quantities of several microns-long 3-10 nm diameter Au nanowires with aspect ratios exceeding 1000 were synthesized in a microwave-stimulated solvothermal approach by reducing chloroauric acid with oleylamine in hexane. This process is easily scaled up to get gram quantities of 80% nanowires in minutes, with the rest of the product comprised of smaller aspect ratio nanostructures and aggregates. The wires are frequently looped or bent indicating high flexibility. We obtained the composites with low volume fractions of fillers (1.2-8%) by dispersing the nanostructures in polydimethylsiloxane, evaporating the solvent and curing at 150 °C. The thermal properties of nanocomposites with different volume fraction fillers were measured in a modified ASTM D5470-06 standard set up. Our poster will discuss the trends in the thermal properties as a function of nanowire filling fraction, and nanowire size, and describe the observed trends in terms of an empirical model.
9:00 PM - DD4.28
Novel Supercapacitor Electrode Materials.
Manoj Ram 1 3 , Farah Alvi 2 , Punya Basnayaka 2 , Yogi Goswami 3 , Lee Stefanakos 3 , Ashok Kumar 1 2
1 Nanotechnology Research and Education Center, University of South Florida, Tampa, Florida, United States, 3 Center Energy Research Center, University of South Florida, Tampa, Florida, United States, 2 University of South Florida, Department of Mechanical Engineering, Tampa, Florida, United States
Show AbstractSupercapacitors are high efficiency energy storage devices representing an attractive alternative for portable electronics and automotive applications due to their high specific power and extended life. There is always a search for new materials to meet the requirements of high power density and long durability supercapacitor devices for new demanding applications. The carbon nanotubes, metal oxides, graphene (G) and conducting polymers have been used in electrochemical supercapacitors as electrode materials. Among them, conducting polymers such as polypyrrole (PPY), polyaniline (PANI) and polythiophene (PTh), polyethenedioxythiophene (PEDOT) are widely considered for redox supercapacitors due to their excellent electrochemical behaviors. The high power supercapacitor is a challenge to build from simply using conducting polymer because of exhibition of poor stabilities during the charge/discharge process, whereas the activated carbon and carbon nanotubes based capacitance is limed due to their microstructures. The nanoporous composite of Carbon Nanotubes (CNTs) and PPy, PANI–inorganic nanocomposites, graphite/PPy composites, p-doped poly (3-methylthiophene) (PMeT)/activated carbon systems, graphene (G)-PANI and RuO2/PPy have been fabricated. We have fabricated G-PANI, G-substituted polyaniline and G-Polythiophene, G-polyethylenedioxythiophene nanocomposite materials. The nanocomposite materials were characterized keeping in view the supercapacitor applications. The G-conducting polymer nanocomposite materials maintain their high conductivity at all times throughout the various redox processes taking place during their charge/discharge cycles, respectively. We have explored various synthesis routes with the aim of maximizing charge transport and transfer between the different species that form the conducting nanocomposite with graphene. The low resistivity, tunable potential window and faster charge transfer rates of the electrodes are needed to have high performance supercapacitor. A specific capacitance of 300 to 500 F/g at a current density of 0.1A/g was observed for G-PANI G-substituted PANI and G-PEDOT electrodes have shown the specific a value of 374 F/g. The G-PPY and G-PTh electrodes have shown the specific capacitance at around 160 F.g−1 and 150 F/g at a current density of 0.75 A/g and 0.25 A/g. The scope of this work is to compare the specific capacitance, stability and life cycle of the various G-conducting polymer nanocomposite materials for supercapacitor applications. This study provides a fundamental understanding for high performance organic electronic devices based on graphene –conducting polymer nanocomposite systems. Based on experimental data shown in this work, we believe that G-conducting polymer capacitor technology could be viable, and could surpass existing technologies when such supercapacitor electrode will be fabricated from novel composite material.
9:00 PM - DD4.29
Tactile Sensing Using Contact Resistance with a Carbon Nanotube Polymer Composite.
Ian McKelvey 1 , Felipe Chibante 2 1 , Arpad Kormendy 2
1 Chemistry, University of New Brunswick, Fredericton, New Brunswick, Canada, 2 Chemical Engineering, University of New Brunswick, Fredericton, New Brunswick, Canada
Show AbstractA carbon nanotube polymer composite has been used to develop a flexible multitouch tactile sensor. Rather than employing the inherent piezoresistive properties of the nanotube polymer, the contact resistances between the polymer and electrodes in various arrangements are exploited to achieve pressure measurements with fast response from small external loadings. Several variables have been examined in order to maximize the efficiency of the response, including sensor size, shape, orientation and grid layout. The nanotube polymer consists of multi-walled carbon nanotubes embedded in a silicone polymer matrix. Material considerations have been explored in order to achieve optimal conductivity for contact resistance as well as to tune other physical features. The final prototype is a flexible sensor that can measure force levels in the finger touch pressure range on multiple points simultaneously using a single polymer sheet and patterned electrode arrangement.
9:00 PM - DD4.3
The Impact of Nanoparticle Size and Shape on Surface Segregation in Polymer Nanocomposites.
Mary Mutz 1 , Mark Dadmun 1
1 Chemistry, University of Tennessee, Knoxville, Tennessee, United States
Show AbstractThe addition of a nanoparticle to a polymer matrix can dramatically alter its bulk mechanical, electrical and thermal properties. Much less well studied is the role of nanoparticle presence on the surface structure, dynamics and properties of the resultant mixture. With this in mind, neutron reflectivity was used to study the impact of nanoparticle presence on the surface segregation of deuterated polystyrene in a polystyrene matrix. The impact of the presence of single-walled carbon nanotubes, graphene sheets, and soft nanoparticles, composed of cross-linked polystyrene and divinyl benzene on the surface segregation process and ultimate structure were examined. The presentation will include a detailed discussion of the impact of molecular shape and specific interactions, as well as other factors, on the resultant interfacial width and excess dPS at the surface (Z*) in these thin film systems.
9:00 PM - DD4.4
Stretchable Nano Brick Wall Gas Barrier Assemblies.
Morgan Priolo 1 2 , Kevin Holder 3 , Jaime Grunlan 1 2
1 Materials Science & Engineering, Texas A&M University, College Station, Texas, United States, 2 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 3 Chemistry, Texas A&M University, College Station, Texas, United States
Show AbstractThin films of sodium montmorillonite clay and weak polyelectrolytes were prepared by alternately dipping a PET substrate into four different dilute aqueous mixtures (poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA), polyethylenimine (PEI), and montmorillonite (MMT) clay). PEO/PAA films are known to exhibit elastomeric behavior, whereas PEI/MMT films have been shown to exhibit highly uniform, ultrathin gas barrier behavior. The combination of these two recipes in a quadlayer assembly has resulted in a stretchable, clay-filled nanocomposite thin film. Films that have endured 30% strain at a rate of 20 in./min. maintain a smooth surface (via SEM), suggesting highly elastic behavior. With an optical transparency of 95% (via UV-Vis) and an aligned nano brick wall structure (via TEM) indicative of good barrier behavior, these films are expected to be a solution for a variety of stretchable and flexible barrier applications, such as flexible electronics and microwaveable food packaging.
9:00 PM - DD4.5
Super Gas Barrier of All-Polymer Layer-by-Layer Assemblies.
You-Hao Yang 1 , Merid Haile 2 , Yong Tae Park 3 , Frank Malek 1 , Morgan Priolo 4 3 , Jaime Grunlan 3 1 4
1 Chemical Engineering, Texas A&M University, College Station, Texas, United States, 2 Chemistry, Texas A&M University, College Station, Texas, United States, 3 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 4 Materials Science & Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractLayer-by-layer assembly of cationic polyethylenimine (PEI) and anionic poly (acrylic acid) (PAA) was investigated with regard to pH of each polymer during deposition. Thickness and surface roughness can be altered dramatically due to the pH-responsive morphology of PEI and PAA. A 10-bilayer film exhibits an oxygen transmission rate below the detection limit of commercial instrumentation (<0.005 cm^3/((m^2 day atm)), even at 100% RH. The oxygen permeability of an 8-bilayer, glutaraldehyde-crosslinked film (only 305 nm thick) is below 3.2×10^-21 cm3 cm/(cm^2 s Pa), which is believed to be the lowest permeability of an all-polymer system ever reported. This relatively simple recipe may be of use for a variety of packaging applications, including flexible electronics that require high flexibility and transparency.
9:00 PM - DD4.6
Influence of Clay Spacing on Gas Barrier Nano Brick Wall Thin Films.
Morgan Priolo 1 3 , Kevin Holder 2 , Jaime Grunlan 3 1
1 Materials Science & Engineering, Texas A&M University, College Station, Texas, United States, 3 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 2 Chemistry, Texas A&M University, College Station, Texas, United States
Show AbstractThin films of montmorillonite (MMT) clay and weak polyelectrolytes were prepared by alternately dipping a PET substrate into different dilute aqueous mixtures of poly(allyl amine) (PAAm), poly(acrylic acid) (PAA), and (MMT). The number of PAAm/PAA layers deposited between clay layers was altered to investigate the effect clay layer spacing has on gas barrier behavior. Film growth, which is expedited by decreasing polymer dip times to only 5 seconds, is shown to be entirely tunable based on PAAm/PAA bilayers. Films created with 2.5, 11.5, 21.5, and 31.5 polymer bilayers exhibit thicknesses of approximately 4, 12, 23, and 58nm between clay layers, respectively. Oxygen transmission rate and clay concentration of these films are shown to dramatically decrease as a function of increasing clay layer spacing, whereas film transparency and nanostructure alignment are virtually unaffected. This study aims to optimize these nano brick wall films for use in a variety of packaging applications.
9:00 PM - DD4.7
Reduced Graphene Oxide/Poly(Dimethylsiloxane) Composites for Use in Finger-Sensing Piezoresistive Pressure Sensors.
Jihun Hwang 1 , Jaeyoung Jang 1 , Tae An 1 , Seonuk Park 1 , Chan Park 2 , Chan Park 1
1 , Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 , POSCO Technical Research Laboratory, Pohang Korea (the Republic of)
Show AbstractWe fabricated a piezoresistive composite using reduced graphene oxide (RGO) as a conductive filler and polydimethylsiloxane (PDMS) as a polymer matrix, which operated in the extremely small pressure range required for finger sensing. To achieve a homogeneous dispersion of RGOs in PDMS, the RGOs were modified by end-functional additives. The percolation threshold of the composites was significantly lowered by the presence of end-functional additives. The electrical conductivity and piezoresistive sensitivity of the composite were found to depend on the additive concentration. The well-dispersed RGOs/PDMS composite showed good piezoresistive characteristics in the 0~100 kPa pressure range.
9:00 PM - DD4.8
Electronic Transport in Organic Memories of Chitosan/Gold Nanoparticles.
German Ayala 1 , Luci Cristina Vercik 1 , Thiago Antonio Menezes 1 , Andres Vercik 1
1 Basic Sciences Department - FZEA, Universidade de Sao Paulo, Pirassununga - SP Brazil
Show AbstractOrganic materials have been studied over time because their applications in electronic and optoelectronic devices, such as organic light emitting diodes, organic field effect transistors, organic memory devices, organic solar cells, sensors and biosensors. Organic material devices present characteristics such as flexibility, low fabrication cost and versatility, associated to the material chemical structure. Although no substitution of traditional silicon devices is expected, organic memory presenting the bistability, i.e., ‘ON” and ‘OFF’ states associated to high- and low- conductivities of the material, have attracted much attention during the past years.The incorporation of nanoparticles (NPs) to polymeric materials has led to devices showing an abrupt increase of conductivity of several orders of magnitude during the writing process of electrical erasable memories. Properties of NPs depend on their size, shape distribution and composition, many of which are controlled by the chemical nature and assembly procedure. The variation of these parameters leads to a broad range of charge transport behavior patterns. Chitosan can be obtained by partial deacetylation of chitin and is extensively used in pharmaceutical and food industries. Films of chitosan with gold nanoparticles (AuNPs) have also been used for immobilization of bio-receptors in biosensors. Chitosan can also be used as reduction agent for NPs synthesis in easy one-step fabrication processes. In this work, the charge transport in chitosan films with different concentrations of AuNPs was studied. The current-voltage curves showed that the conductivity of the films is modulated by the presence of nanoparticles, with higher measured values as the nanoparticle concentration is increased. The current flowing in organic devices is controlled either by the injection of charge from the electrodes or by the transport in the organic bulk. The dominant limiting mechanism, which will determine the dependence of current on voltage, is still under intense debate. The injection could occur by thermoionic emission or by tunneling. The transport in the organic bulk could occur in two regimes: space-charge limited current (SCLC) and trap-charge limited current (TCLC). A linear dependence observed in a double-logarithmic plot of the current versus voltage curves, suggests that the transport in the studied samples occurs in the TCLC regime, which predicts a slope dependent on the trap decay energy.Hysteresis in the current-voltage curves was also observed in the studied material and was attributed to capture electrons in traps, in good agreement with the fitting transport model. These results indicate that bistability in chitosan films can be controlled by the introduction of NPs. This behavior is reported in this work for the first time for this material and could be used in organic memories of chitosan/AuNPs, organic transistors or enzyme field effect transistors.
9:00 PM - DD4.9
PLA Based Nanocomposites: Effect of Filler Reinforcement on Polymer Thermal Properties, Chain Orientation, and Electrical Conductivity.
Qian Ma 1 , Erika Simona Cozza 1 2 , Bin Mao 1 , Orietta Monticelli 2 , Qiaobing Xu 3 , Peggy Cebe 1
1 Physics, Tufts Unversity, Medford, Massachusetts, United States, 2 Dipartimento di Chimica e Chimica Industriale, Università di Genova, Genova Italy, 3 Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, United States
Show AbstractPhase structure and orientation behavior were investigated for electrospun polylactic acid (PLA) nanocomposite fibers incorporating graphene, or carbon nanotubes, as fillers. Highly-aligned fibers were developed by adopting a high-speed rotating wheel compared to random in-plane alignment obtained using stationary counter-electrode plates. The filler-matrix interaction was studied through quantitative thermal analysis to evaluate the confinement induced by different fillers on the mobile polymer chain around fillers. The orientation distribution of both the molecular chains and the anisotropic fillers along the fiber axis was investigated using 2-D real-time synchrotron wide angle X-ray scattering, polarized infrared spectroscopy, and molecular retraction experiments. Anisotropic fillers are found to increase molecular chain extension and improve fiber orientation, leading to improvement in transport properties. Investigation is presently underway of the improvement in electrical conductivity of PLA fibers, induced by the graphene nanofiller, with the potential to enhance neural cell function for neural tissue engineering applications. This research was supported by the National Science Foundation, Polymers Program of the Division of Materials Research, through grant DMR-0602473.
Symposium Organizers
Jaime Grunlan Texas A&M University
Sergei Nazarenko The University of Southern Mississippi
Jeff Bahr Nanocomposites, Inc.
Eliane Espuche University Claude Bernard Lyon 1
Symposium Support
Schlumberger, Bayer, Tyco Electronics, 3M
DD5: Nanocomposite Sensors
Session Chairs
Eliane Espuche
Brian Landi
Tuesday AM, November 29, 2011
Room 201 (Hynes)
9:00 AM - DD5.1
Resistive Switching in Bulk Ag Nanowire/Polymer Composites.
Jamie Ford 1 , Sadie White 1 , Karen Winey 1
1 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractBulk composites of electrically conductive nanoparticles within an insulating polymer matrix are insulating when the conductive particle concentration is below the electrical percolation threshold and conductive above it. However, we have observed reversible resistive switching with increasing voltage at room temperature in Ag nanowire/polystyrene composites with nanowire concentrations close to the percolation threshold. We have found the reversibility of the observed switching behavior to be temperature dependent which implies a diffusive process is involved. We propose the basis for resistive switching in these materials is the formation of field-induced filaments between adjacent nanowires that extend the percolated electrical network and increase the overall conductivity of the system. Here, we will compare our observations of resistive switching in Ag nanowire/polystyrene and Ag nanowire/poly(methylmethacrylate) bulk nanocomposites and explore the breadth of metal nanowire and polymer systems that exhibit resistive switching.
9:15 AM - DD5.2
Mechanism for the Electrode-Sensitive Resistive Switches of Polymer:Metal Nanoparticle Memristors.
Jianyong Ouyang 1
1 Department of Materials Science & Engineering, National University of Singapore, Singapore Singapore
Show AbstractResistive switches have been observed on devices with polymer/metal nanoparticle composites. These devices can be used as memory devices and called as memristors. This paper will report memristors with composites of a polymer blended with gold nanoparticles capped with conjugated organic ligand. These memrisotrs exhibit electrode-sensitive bipolar resistive switches. The electrode-sensitive switches are attributed to the charge transfer between metal nanoparticles and an electrode and the electric field-induced charge transfer between the core and the orgnaic ligand of the metal nanoparticles.
9:30 AM - DD5.3
Carbon Nanotube Reinforced Sensitive Piezo-Resistive Elastomer Composite Film for Sensors.
Noe Alvarez 1 , Victor Martinez 1 , Manuel Quevedo-Lopez 1 , Jeffrey Bahr 2
1 Material Science Engineering, University of Texas at Dallas, Richardson, Texas, United States, 2 , Nanocomposites Inc., The Woodlands, Texas, United States
Show AbstractAs applications for carbon nanotubes (CNTs) in commercial products grows, new applications from research studies continue to arise. The unique properties such as mechanical strength, surface area, length-diameter ratio and electrical conductivities of the CNTs have no parallel in material science. CNT enhanced composites comprising different polymer matrices have been extensively reported; one of the more intriguing comprising stretchable, conducting composites. CNT enhanced flexible and stretchable conducting polymers have great potential in electronic skin applications and sensors. We report our recent progress towards development of a sensitive piezo-resistive composite film or membranes with up to five orders of magnitude electrical resistance change upon mechanical deformation as a result of applied force. Applied force within a 25 Newton range generates mechanical deformation of the elastomeric membrane and thereby alters membrane electrical resistance by increasing the contact between the CNTs dispersed within the polymer. We have coupled our piezoresistive elastomer nanocomposite membrane with flexible electronics (Schottky diode array) that will ultimately be capable of high resolution in terms of locating the applied force. Due to sensitivity, flexibility and the robustness of the composite material, there are a large number of potential sensor application. The plot below shows example performance of a membrane under applied compressive force.
9:45 AM - **DD5.4
Melt Mixed Polymer-MWCNT Composites for Liquid Sensing Applications.
Petra Poetschke 1 , Tobias Villmow 1 , Sven Pegel 1 , Andreas John 1 , Rosina Rentenberger 1
1 , Leibniz Institute of Polymer Research Dresden, Dresden Germany
Show AbstractPolymer/Carbon nanotube (CNT) composites show next to improved mechanical, thermal, and electrical properties also sensitivity to external stimuli. A detection of environmental condition changes is possible, if it affects the electrically conductive CNT network inside the insulating polymer matrix. In case of liquid sensing, swelling of the polymer matrix due to contact with organic liquids and interactions between solvent molecules and CNTs result in a local gap enlargement between individual CNTs and/or CNT clusters, resulting in a detectable increase of electrical resistance. Accordingly, CNT based conductive polymer composites (CPCs) represent very promising candidates for the design of smart components capable of integrated monitoring. In this presentation we focus on their use as leakage detectors for organic solvents.The sensor concept, as well as the underlying mechanism, is demonstrated for polycarbonate (PC)/CNT based CPCs on compression-moulded samples. The selectivity as an important sensor property will be discussed in context with the Hansen solubility parameters and the solvent molecule’s size. The time dependent electrical response characteristic upon immersion depends on the diffusion kinetics of the specific solvent molecules into the CPC. A model allowing the calculation of the time depending relative resistance change is presented considering several factors like the diffusion parameters, composite characteristics like initial resistance and geometrical values of the sensing sample. Using this model, Rrel curves of PC/MWCNT composites were simulated which fit very well the experimental data.In order to examine the production of first prototype large area sensors, fibres and textiles based on composites of different polymer matrices with multiwalled carbon nanotubes (MWCNT) were produced. MWCNT containing fibres based on poly lactic acid (PLA) and polycaprolactone (PCL)/ polypropylene (PP) blends were produced by melt spinning and textile fabrication was performed for PCL/PLA blends. For all presented composite systems the electrical response characteristics was analysed for various organic solvents.
10:15 AM - DD5.5
Conductive Polymer Composites Based Sensors for Detection and Discrimination of VOCs.
Mickael Castro 1 , Bijandra Kumar 1 , Jianbo Lu 1 , Jean Francois Feller 1
1 LimatB, European University of Brittany, Lorient France
Show AbstractVolatile organic compounds, identified as hazardous agents, are major concern for both environment and human health. Detection, discrimination and quantification of VOC in atmosphere can help to assess human exposure levels and evaluate ambient environmental contaminant distribution. Furthermore, the analysis of specific VOC from exhaled breath provides clues regarding metabolic and physiological activities of a person, and can represent a non-invasive anticipated diagnosis for certain diseases. Therefore, the development of electronic noses from an array of non-specific chemical sensors, controlled and analyzed electronically, mimicking the mammalian nose, is of great interest. Conductive Polymer nanoComposites (CPC) obtained by dispersing conducting nanofillers, in this case carbon nanotubes (CNT), into insulating polymer matrices, are attractive for vapor sensors development because of their good environmental stability, good sensitivity, fast response time, good reproducibility and low operating temperature. In this work, CPC sensor materials were developed by the layer-by-layer spraying process of CNT–polymer solution. Morphology of the composites was characterized at different scales and chemo-electrical properties were investigated in the presence of different solvents at room temperature. Results have shown that vapor sensing properties of the obtained samples are related to different parameters such as filler content, vapor nature, thickness of samples and vapor flow rate. Finally, we investigated the ability of an e-nose composed of an array of CNT-based CPC sensors to discriminate a set of selected organic solvents using a classical recognition technique.
10:30 AM - DD5.6
Electrical Conductivity of Anisotropic iPP Carbon Nanotube Thin Films.
Georgi Georgiev 1 2 , Gajinder Hoonjan 1 , Ananta Adhikari 1 , Germano Iannacchione 3 , Peggy Cebe 2
1 Natural Sicences, Assumption College, Worcester, Massachusetts, United States, 2 Physics and Astronomy, Tufts University, Medford, Massachusetts, United States, 3 Physics, Worcester Polytechnic Institute, Worcester, Massachusetts, United States
Show AbstractCarbon nanotubes (CNTs) and polymer nanocomposites exhibit many properties that are not present in the pure polymers. Their crystallization kinetics and crystal forms are greatly changed by the nanotubes. Carbon nanotubes are conductive while the polymer films are insulators. In our research we explore the effects of different concentrations of carbon nanotubes on the electrical conductivity of thin films of Isotactic Polypropylene (iPP). iPP is itself one of the most widely used polymers, and it is expected that results will be widely used in many polymer applications, some of which are for flexible electrodes, medical and electronics packaging and chemical sensors. Anisotropy of polymer films with CNTs and polymer crystals preferably oriented in one direction provides an opportunity to create an anisotropic electrical conductivity of the polymer films, higher in the direction of the alignment and lower in the direction perpendicular to it. We explore different concentration of CNTs in iPP: 0.01%, 0.1%, 1%, 2% and 5% CNTs. iPP and CNTs exhibits liquid crystalline order and their liquid crystal directors couple. The iPP/CNT films were sheared in the melt state at 200°C and 1Hz. The sheared samples were analyzed using polarized optical microscopy (POM) and Two Dimensional Microscopic Transmission Ellipsometry (2D-MTE) to measure anisotropy. During shearing we detected a sudden increase of birefringence at 151°C in the samples, higher than the iPP crystallization temperature, indicating liquid crystalline ordering. We measured anisotropic 2D-WAXS patterns of the samples that contained CNTs, indicating strong ordering of the crystals. Our results indicate that CNTs couple to the smectic phase of iPP, improve its order upon shearing and the crystals created after the formation of the oriented smectic phase are strongly aligned parallel to the direction of shearing.
10:45 AM - DD5.7
Network Formation and Electrical Conduction in Carbon Nanotube Modified Polymers.
Cyrill Cattin 1 , Pascal Hubert 1
1 Department of Mechanical Engineering, McGill University, Montreal, Quebec, Canada
Show AbstractCarbon nanotube (CNT) addition to polymers allows for the design of electro-conductive polymer nanocomposites [1]. With the formation of an electrically conducting network throughout the electrically non-conducting polymer matrix, the CNTs enable electron flow through the material. Due to their outstanding electrical properties and high aspect ratio, small quantities of CNTs can induce a significant improvement in the electrical conductivity, without significant compromises on other material properties of the host polymer, such as its mechanical and optical properties. It has been shown that CNT network formation in CNT/polymer nanocomposites is strongly dependant on the material processing conditions [2]. Through rearrangement of CNTs, movement of the latter prior to polymerization allows for the formation of an electrically conducting network at filler concentrations below the statistical percolation threshold. CNT/polymer nanocomposites with an optimized network structure have the potential for improved electrical performance, which is critical for the use of such materials in sensing applications. In the present research we monitor CNT network formation in multi-walled CNT modified polydimethylsiloxane prior to and during polymerization, and we analyze the influence of the final CNT network structure on the electrical conduction mechanism. Network formation is traced in real-time by means of simultaneous rheological and electrical characterization. Processing induced network formation is observed and analyzed as a function of CNT concentration. In addition, the alternating voltage method is used to analyze in real-time the current-voltage characteristics of the material as a function of degree of polymerization. Overall, a clear non-ohmic behaviour is observed. For CNT concentrations below the statistical percolation threshold, both the electrical resistivity and the voltage dependence of the sample resistance increase with the degree of polymerization, which indicates CNT separation during polymerization. It is proposed that the electrical conduction mechanism in CNT/polymer nanocomposites is a combination of ohmic conduction and electron tunnelling through insulating polymer layers. The interdependence of electrical resistance and tensile and compressive strain is measured to further evaluate both the relative magnitude of the two conduction mechanisms and the multifunctionality of CNT/polymer nanocomposites. References: [1] J. N. Coleman, S. Curran, A. B. Dalton, A. P. Davey, B. McCarthy, W. Blau and R. C. Barklie, Phys Rev B 58 (1998), p. R7492. [2] J. Z. Kovacs, B. S. Velagala, K. Schulte and W. Bauhofer, Compos Sci Technol 67 (2007), p. 922.
11:00 AM - DD5: Sensors
BREAK
11:30 AM - **DD5.8
Diffusion Behaviours in Conductive Polymer Nanocomposite CPC Sensors Architectured by Combining Layer by Layer Assembly and Segregated Networks Strategy.
Jean-Francois Feller 1 , Jaime Grunlan 2 , Hyoung Jin Choi 3
1 LIMATB-UBS, European University of Brittany (UEB), Lorient, Bretagne, France, 2 Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 3 Polymer Science & Engineering, Inha University, Incheon Korea (the Republic of)
Show AbstractConductive Polymer nanoComposites (CPC) transducers prepared from the dispersion of carbon nanofillers into an insulating polymer matrix have been successfully used to develop volatile organic compounds VOC sensors under various shapes for many applications, evidencing the versatility of such systems 1-7. Nevertheless CPC chemoresistive properties can be difficult to reproduce without structuring strategies. Besides structuring hierarchically the conducting network in three dimensions using a spray layer by layer sLbL process was found to be an effective way to both control the composite architecture and enhance the sensor response by increasing the specific surface accessible to analyte molecules 8-12. More recently the combination of sLbL with segregated networks generated by smooth acrylate latexes 13 and hard poly(methyl methacrylates) 14 were found to open new prospects in the control of the disconnection of carbon nanotubes junctions leading to quantum tunnelling conduction variation.Segregated networks of CNT are found to give transducers with quantitative responses when exposed to VOC that can be considered as a sorption isotherm and very well fitted with a Langmuir-Henry-Clustering (LHC) diffusion model. This model gives a new insight into understanding of chemo electrical behaviour of CPC and appears to be helpful to optimise sensor design by tailoring transducer initial characteristics to suitable solvent vapour fraction measurement range. Moreover, sensors selectivity is discussed in terms of χ12 the Flory-Huggins polymer/solvent interaction parameter, δp, εr and d, respectively the polar component of solubility parameter, the dielectric permitivity and the molecules size of solvents.References1.J. Chen, N. Tsubokawa, Polym. Adv. Tech., 2000, 11, 101-107.2.M. E. Koscho, R. H. Grubbs, N. S. Lewis, Anal. Chem., 2004, 74 1307-1315.3.J. F. Feller, Y. Grohens, Sens. & Actua. B: Chem., 2004, 97, 231-242.4.X. M. Dong, R. W. Fu, M. Q. Zhang, B. Zhang, M. Z. Rong, Carbon, 2004, 42, 2551-2559.5.J. F. Feller, D. Langevin, S. Marais, Synth. Met., 2004, 144, 81-88.6.J. K. Abraham, B. Philip, A. Witchurch, V. K. Varadan, C. C. Reddy, Smart Mater. Struct., 2004, 13, 1045-1049.7.K. Zribi, J. F.Feller, K. Elleuch, A. Bourmaud, B. Elleuch, Polym. Adv. Tech., 2006, 17 727–731.8.J. F. Feller, H. Guézénoc, H. Bellégou, Y. Grohens, Macro. & Symp., 2005, 222, 273-280.9.J. F. Feller, Y. Grohens, Synth. Met., 2005, 154, 193-196.10.A. Bouvrée, J. F. Feller, M. Castro, Y. Grohen, M. Rinaudo, Sens. & Actua. B, 2009, 138, 138-147.11.M. Castro, J. Lu, S. Bruzaud, B. Kumar, J. F. Feller, Carbon, 2009, 47, 1930-1942.12.J. Lu, B. Kumar, M. Castro, J. F. Feller, Sens. & Actua. B, 2009, 140, 451-460.13.J. Lu, J. F. Feller, B. Kumar, M. Castro, Y. S. Kim, Y. T. Park, J. C. Grunlan, Sens. & Actua. B, 2011, 155, 28-36.14.J. F. Feller, J. Lu, K. Zhang, B. Kumar, M. Castro, N. Gatt, H. J. Choi, J. Mater. Chem., 21, 4142-4149 (2011).
DD6: Ionic/Proton Conductivity I
Session Chairs
Mark Ellsworth
Rosario Gerhardt
Tuesday PM, November 29, 2011
Room 201 (Hynes)
12:00 PM - **DD6.1
Ordered Solid-Liquid Nanocomposites with Enhanced Li Ion Conductivity Properties Based on the Polymerization of Non-Aqueous, Self-Asssembled Lyotropic Liquid Crystals.
Douglas Gin 1 2 , Robert Kerr 2 , Julian Edwards 2 , Richard Shoemaker 2 , Seth Miller 3 , Brian Elliott 4
1 Dept. of Chem. & Biol. Engineering, University of Colorado, Boulder, Colorado, United States, 2 Dept. of Chem. & Biochem., University of Colorado, Boulder, Colorado, United States, 3 , TDA Research, Inc., Wheat Ridge, Colorado, United States, 4 , Heron Scientific, Inc., Englewood, Colorado, United States
Show AbstractA nanostructured, liquid-filled, polymer electrolyte material for use in Li batteries has been prepared via the polymerization of lyotropic (i.e., surfactant) liquid crystal (LLC) assemblies. This material is based on a lithium sulfonate surfactant monomer that self-assembles into a type II bicontinuous cubic phase in the presence of liquid propylene carbonate (PC) and its Li-salt solutions. The resulting cross-linked but flexible polymer nanocomposite has ordered, 3D-interconnected liquid PC nanochannels and a room-temperature ion conductivity of 10^–4 to 10^–3 S/cm when formed with 15 wt % (0.245 M LiClO4-PC) solution. Liquid-like diffusion in the nanochannels and good ionic conductivity (ca. 10^–4 S/cm) are retained down to –65 °C. This ion conductivity value also remains steady at temperatures at over 55 °C. Working Li-metal batteries with voltages in the 3.5 V range have been successfully made using this material. Studies varying the amount and type of liquid electrolyte, free Li salt, etc. to optimize ion conductivity values and battery performance will also be discussed.
12:30 PM - DD6.2
Hybrid Ion Conducting 3D Nanofillers for Solid Polymer Electrolytes in Lithium Ion Batteries.
Haleh Ardebili 1 , Changyu Tang 2 , Ken Hackenberg 2 , Pulickel Ajayan 2
1 Mechanical Engineering, University of Houston, Houston, Texas, United States, 2 Mechanical Engineering and Materials Science, Rice University, Houston, Texas, United States
Show AbstractThere is a growing shift towards replacing liquid with polymer electrolytes due to many advantages of polymers including enhanced safety and flexibility. However, ionic conductivity of polymers can be orders of magnitude lower than that of liquid electrolytes. Nanoscale fillers are known to enhance the Li ion conductivity as well as improve the mechanical properties of the polymer electrolytes. Carbon nanotubes (CNTs) can be highly effective in improving the mechanical properties of the polymer but are electrically conductive and can pose the risk of shorting in batteries. In this study, we show that carbon nanotubes grown and packaged within clay layers can work as effective hybrid 3D nanofillers as the nanotubes are electrically insulated by the clays. We show, for the first time, that such hybrid nanofillers improve the Li ion conductivity of PEO electrolyte by almost two orders of magnitude. Furthermore, the incorporation of only 5% clay-nanotube hybrid particles leads to 160% increase in the tensile strength of the polymer electrolyte. The mechanism of ion conductivity enhancement can be attributed to the high surface density of the 3D hybrid fillers and the strong interaction between the CNT’s rich negative electron cloud and positive lithium ions.
12:45 PM - DD6.3
Transport Properties of Nanoparticle-Oligomer Hybrid Composite Electrolytes.
Jennifer Schaefer 1 , Lynden Archer 1
1 Chemical Engineering, Cornell University, Ithaca, New York, United States
Show AbstractSignificant effort has been devoted to the development of advanced electrolytes for use in lithium batteries, such as polymers, gels, inorganic-polymer composites, inorganic-liquid composites, hybrids, and ionic liquids. We report on the development of a novel nanoparticle-organic hybrid composite platform, whereas inorganic nanoparticles are functionalized with an oligomeric corona and then dispersed in a host. Silica nanoparticles were functionalized by reaction with trimethoxysilane terminated PEG, diluted in various ratios with PEGDME, and doped to 1M LiTFSI in the organic phase. This yielded a family of composite electrolytes with varying silica volume fractions, φ, ranging from liquids to gels to solids. Even at high φ, the particles were uniformly dispersed and unagglomerated, producing an electrolyte with a nanoporous network of ion channels. Transport properties of the nanocomposite electrolytes were studied as a function of φ. Normalization of ionic conductivity data to a reduced temperature form reveals that after accounting for differences in glass transition temperature among the composites, the ionic conductivity is a linear function of φ. Thermal and ionic conductivity in particle composites have been studied by several groups, using a framework proposed by Maxwell. In this model, the effective conductivity, σ, of a homogeneous suspension of particles of conductivity, σp, volume fraction, φ, dispersed in a medium of conductivity, σ0, can be computed using the simple formula, σ/σ0 = 2(1- φ )/(2+ φ ) in the limiting case where the particles are perfect insulators at infinite dilution. For our system, this relationship holds to large values of φ; however, the front-factor is 3.5 rather than 2, which implies that the nanohybrids are in fact hindering conductivity by more than a space-filling proportion. This may be attributed to the tethered PEG chains interacting with dissociated ions that would otherwise freely diffuse with the plasticizer.The mechanical properties of the composite electrolytes vary drastically from the transport properties. Most notably, at φ = 0.29, the materials transitioned from liquid-like to gel-like, and there was a sharp increase in the mechanical modulus of the material with only slight decreases in ionic conductivity. This is due to particle jamming. Thus, these materials have a significant yield stress without compromise in conductivity. Our newest work focuses on exploiting this nanocomposite platform by using particles functionalized with non-interacting ligands to improve conductivity or with charge bearing ligands to improve Li+ transference. Ref: J.L. Schaefer, S.S. Moganty, D.A. Yanga, L.A. Archer, J. Mater. Chem. 2011
DD7: Ionic/Proton Conductivity II
Session Chairs
Jianyong Ouyang
Daniel Schmidt
Tuesday PM, November 29, 2011
Room 201 (Hynes)
2:45 PM - DD7.1
Proton Exchange Membrane Synthesized by Pore-Filling Polymerization Technique.
Liang Hong 1 , Siok Wei Tay 2
1 , National University of Singapore, Singapore Singapore, 2 , Institute of Materails Research and Engineering, Singapore Singapore
Show AbstractProton exchange membrane with interconnected H+-transfer channels in submicron scale has been fabricated by means of pore filling polymerization. Polysulfone (PSU) membrane containing densely distributed pores is synthesized using the phase inversion approach. The membrane is then filled up with a designed formula consisting of monomers (e.g. 2-acrylamido-2-methylpropane sulphonic acid and N, N’-Methylenebisacrylamide) and a binary solvent. It is undertaken through solution diffusion of the monomer formula into the pores impregnated with the bore liquid. When the PSU matrix loaded with monomers is subjected to polymerization, a uniform distribution of interconnected H+-transfer channels is realized. This special membrane structure gives rise to a maximum ionic exchange capacity of 2.43 meq/g and the highest proton conductivity of 0.2 S/cm. Compared to the commercial Nafion® membrane, the pore-filled membrane significantly enhances the power output of H2-PEM fuel cell.
3:00 PM - **DD7.2
Layer-by-Layer Coating of Thin Films for Improved Electrical Energy Storage.
Anne Dillon 1 , Yoon Seok Jung 1 , Chunmei Ban 1 , Pung Lu 2 , Stephen Harris 2 , Andrew Cavanagh 3 , Steven George 3 , Se-Hee Lee 3
1 , National Renewable Energy Laboratory, Golden, Colorado, United States, 2 , General Motors, Warren, Michigan, United States, 3 , University of Colorado, Boulder, Colorado, United States
Show AbstractSignificant advances in both energy density and rate capability for Li-ion batteries will be necessary for implementation in next generation electric vehicles (1). By employing metal oxide nanostructures, it is possible to achieve Li-ion anodes that have significantly higher capacity than the state-of-the-art technology. However, because of the large volume expansion it is difficult to achieve stable cycling. We have demonstrated that thin film MoO3 nanoparticle electrodes (~2 µm thick) have a stable reversible capacity of ~630 mAh/g, at C/2 (charge/dicharge in 2 hours). By fabricating more conventional electrodes (~35 µm thick) with conductive additive and binder, an improved reversible capacity of ~1000 mAh/g is achieved but, unfortunately, the rate capability decreases. In order to achieve high-rate capability, we applied a thin layer-by-layer Al2O3 atomic layer deposition (ALD) coating, ~8 Å thick, to enable high volume expansion and prevent mechanical degradation (2). We have also shown that similar ALD Al2O3 thin coatings improve the performance of more conventional electrodes including graphite and LiCoO2. Specifically the coated graphite electrodes were shown to operate efficiently at a high temperature of 55C. Also the LiCoO2 was shown to operate at 4.5 V vs. Li/Li+ where reaction with the electrolyte and cobalt dissolution generally occur (3). More recently, we have performed mechanistic studies including nano-indentation, electrochemical impedance spectroscopy, X-ray photoemission spectroscopy and time of flight secondary ion mass spectrometry to unravel the mechanism of how the Al2O3 coatings on a single electrode dramatically improve the performance of a variety of different materials. We are also exploring layer-by-layer molecular deposition and have found that certain molecules better enhance both ionic and electronic conductivity. The new mechanistic studies will be discussed in detail.1.Dillon, A. C., Chem. Rev. 2011, 110 (11), 6856-6872.2.Riley, L. A.; Cavanagh, A. S.; George, S. M.; Jung, Y.-S.; Yan, Y.; Lee, S.-H.; Dillon, A. C., ChemPhysChem 2010, 11, 2124.3.Jung, Y.-S.; Cavanagh, A. S.; Kang, S.-H.; Dillon, A. C.; Groner, M. D.; George, S. M.; Lee, S.-H., Advanced Materials 2010, 22 2172.
3:30 PM - DD7: Ionic
BREAK
DD8: Nanocomposites for Energy Applications
Session Chairs
Tuesday PM, November 29, 2011
Room 201 (Hynes)
4:00 PM - DD8.1
Polymer/Inorganic Nanocomposites with Tailored Hierarchical Structure as Advanced Dielectric Materials.
Evangelos Manias 1 , Clive Randall 2 , Vivek Tomer 2 , George Polizos 1
1 Materials Science, Penn State University, University Park, Pennsylvania, United States, 2 Materials Research Institute, Penn State University, University Park, Pennsylvania, United States
Show AbstractMost advances and commercial successes of polymer/inorganic nanocomposite rely on simple dispersion of nanoparticles in a polymer matrix. Such approaches leave untapped opportunities where performance can be improved by controlling the larger length-scale structures. Here, selected examples where the hierarchical structure (from millimeter to nanometer) is tailored to control the transport properties of the materials (space charge conductivity, e-tree path upon breakdown) giving rise to marked property enhancements. Examples address dielectrics applicable to high-voltage (power) capacitors, and where the structure is self-assembled, both at the nm and the micron scales, and, thus, can be produced in ton quantities using standard industrial practices. First, an epoxy/Barium-Titanate/clay composite is designed to yield decreased space charge conductivity and a higher permittivity. In a second example, PE blends or PVDF copolymers are reinforced with similar nanofillers and composites are designed with a high orientation which yields marked improvements in breakdown strength under high electric-field.
4:15 PM - DD8.2
Enhancing Power Factor of Polymer Composites Containing Porphyrin-Stabilized Nanotubes.
Gregory Moriarty 1 , Jamie Wheeler 1 , Choongho Yu 1 , Jaime Grunlan 1
1 Department of Mechanical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractPoly(vinyl acetate) copolymer latex-based composites were prepared with multi-walled carbon nanotubes (MWNT), stabilized with sodium deoxycholate (DOC) or meso-tetra(4-carboxyphenyl) porphine (TCPP). SEM images show that a segregated MWNT network developed during drying, which resulted in relatively low percolation thresholds (1.62 and 2.17 wt% MWNT for DOC and TCPP, respectively). The electrical conductivity of TCPP-stabilized composites is very similar to that of DOC-stabilized, while the thermopower (or Seebeck coefficient) is five times as large (5 to 25 µV/K, respectively). This enhanced thermopower suggests the MWNT:TCPP composite will have an order of magnitude greater thermoelectric efficiency. The thermal conductivity also remains comparable to typical polymeric materials (< 0.30 W/(m.K)) due to numerous tube – tube connections that act as phonon scattering centers. The universality of this approach was confirmed using double-walled carbon nanotube-filled composites that showed similar improvement with TCPP stabilization. The tailorability of the Seebeck coefficient with different stabilizing agents is an exciting avenue to increasing the thermoelectric efficiencies of polymer composites.
4:30 PM - **DD8.3
Organic Nanocomposites for Thermoelectric Energy Conversion.
Choongho Yu 1
1 Mechanical Engr./Materials Science & Engr., Texas A&M University, College station, Texas, United States
Show AbstractInorganic semiconductor materials have been intensively studied for thermoelectric energy conversion in the past, but they typically contain heavy, brittle, toxic, expensive elements and require complicated or/and costly manufacturing processes. These disadvantages have been impeded a wide use of thermoelectric systems despite their compactness, silence/robustness due to no-moving parts, and versatility in both refrigeration and energy harvesting. This report presents carbon nanotube-based organic composites that have potentials to alleviate such drawbacks. Typical organic materials have low thermal conductivities that are best suited to thermoelectrics, but their poor electrical properties with strong adverse correlations have prevented them as feasible candidates. Our composites, containing carbon nanotubes, poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate) (PEDOT:PSS), or/and polyvinyl acetate, show thermopowers weakly correlated with electrical conductivities, resulting in large thermoelectric power factors that are orders of magnitude better than those of typical polymer composites. Furthermore, their high electrical conductivities make our composites very promising for various electronic applications. The electrical properties and microstructures of the composites were studied when nanotube and polymer concentrations were altered, and the optimum nanotube concentrations for better power factors were also identified. Despite the high electrical conductivity, the thermal conductivity was close to that of typical polymers. We believe further research utilizing the loosely related transport properties may lead to thermoelectric materials with high performance and easy-manufacturing processes that require only simple mixing and drying methods without any special environments.
5:00 PM - DD8.4
Carbon Nanotube Based Power Thermoelectric Devices.
Thomas Van Vechten 1 , David Lashmore 1 , Ethan Ciccotelli 1 , David Degtiarov 1 , Diana Lewis 1
1 , Nanocomp Technologies Inc, Concord, New Hampshire, United States
Show AbstractLight weight waste heat harvesting electric generators, fabricated from n- and p-type doped carbon nanotube sheets and yarns are investigated. Currently, thermoelectric generators are restricted to narrow niche markets, often centered on systems that are intended to operate un-attended for extended periods. Searching to expand the opportunities in which thermoelectric generators are competitive with alternate power sources, we are developing light weight and robust thermoelectric generators aimed for space, aerospace, and vehicle applications. Material synthesis and processing technologies must be developed which bring the bulk, composite material close to the electrical conductivity and Seebeck coefficient of the properly doped carbon nanotube molecule, while heat transport should be determined by inefficient connections between nanotubes and between bundles. A second requirement in order to exploit the low density (~0.5 g/cm3) of the bulk CNT phase, the generator needs to be connected to the hot and cold reservoirs of the application without massive heat exchangers, which would prevent the device from reaching large power per unit weight ratios. We are pursuing a thermoelectric generator and heat exchanger package in which the high temperature heat collector, the n-type thermoelectric, the p-type thermoelectric, and the low temperature heat radiator are all fabricated from a single continuous tape which is infiltrated with a periodic pattern of dopants and matrix materials. Then by appropriately folding this tape a series of thermoelectric couples can be formed. Since the backbone of the heat exchangers will be a continuous material with the thermoelectric elements we expect less thermal interface resistance which would increase the fraction of the temperature difference present in the application which can be brought to the thermoelectric device. If the product of the thermoelectric conversion efficiency with the harvesting ability of the heat exchangers, divided by the device mass is large enough then this system can be a competitive power source for vehicles in which low mass is a particularly critical concern. Progress towards this challenging goal will be reviewed.
5:15 PM - DD8.5
Functionalized Barium Titanate Nanocomposite Capacitors for Energy Storage.
Kristin Kraemer 1 4 , Susan Cooper 1 4 , Steve Wignall 1 4 , Nicholas Reding 1 4 , Rajesh Krishnan G. 2 4 , Rafal Korlacki 3 4 , James Takacs 2 4 , Stephen Ducharme 1 4
1 Physics and Astronomy, University of Nebraska, Lincoln, Nebraska, United States, 4 Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska, United States, 2 Chemistry, University of Nebraska, Lincoln, Nebraska, United States, 3 Chemical and Biomolecular Engineering, University of Nebraska, Lincoln, Nebraska, United States
Show AbstractTo improve energy storage devices, it is necessary to create new materials with high energy densities. A promising approach is to make polymer nanocomposites containing oxide nanoparticles, thus combining the high dielectric constant of the nanoparticles with the high breakdown strength of the polymer matrix. We will be discussing our results from thin film capacitors consisting of functionalized barium titanate nanoparticles in a polyvinylidene fluoride (PVDF) terpolymer matrix. The nanoparticles have been functionalized by VDF oligomers and alkyphosphonic acids. A key innovation is the use of the VDF oligomers in the PVDF terpolymer matrix since the coating on the particles and matrix will be chemically and electrically compatible with each other. By using the oligomers terminated with the proper end groups, we have attached them to barium titanate nanoparticles and examined the properties of the polymer and particle nanocomposite. Presented will be the dielectric and energy density results of our thin films made by spin coating and Langmuir Blodgett deposition, along with microscopy and spectroscopy results of the composite materials.This work was supported by the Office of Naval Research, the Department of Energy, and the Nebraska Research Initiative.