Padma Gopalan University of Wisconsin-Madison
Qing Wang The Pennsylvania State University
Hilmar Koerner U. S. Air Force Research Lab/RXBN
Dhandapani Venkatraman University of Massachusetts Amherst
Teruaki Hayakawa Tokyo Institute of Technology
JJ1: Supramolecular Assembly of Hybrid Materials I
Tuesday PM, November 30, 2010
Independence W (Sheraton)
9:30 AM - JJ1.1
Graphene Oxide as a Polymerization Initiator and as a Carbon Filler in Composites.
Daniel Dreyer 1 , Sun Hwa Lee 3 , Jeffrey Potts 2 , Rodney Ruoff 2 , Sang Ouk Kim 3 , Christopher Bielawski 1 Show Abstract
1 Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas, United States, 3 Materials Science and Engineering, KAIST, Daejeon Korea (the Republic of), 2 Mechanical Engineering, The University of Texas at Austin, Austin, Texas, United States
Owing to their remarkable electronic and mechanical properties, chemically-modified graphenes (CMGs) have emerged as materials of considerable interest. Graphene oxide (GO) often serves as a common precursor to these materials. Possessing a surface rich in various oxygen-containing functional groups (e.g. alcohols, epoxides, carboxylates), GO can be modified with a variety of reagents that bestow upon it desirable properties, such as improved solubility or mechanical properties. We will present a method that employs GO, or functionalized derivatives thereof, as initiators of various polymerization reactions. The resulting composites show good solubility in a variety of organic solvents, as well as improved mechanical/thermal properties and compatibility of the GO with the polymer. Phase separation and aggregation of the carbon can be avoided in this approach to composite preparation.
9:45 AM - JJ1.2
Predicting Nanostructure of Block Copolymer/Nanoparticle Assemblies with a Field Theoretic Approach.
Kahyun Hur 1 , Richard Hennig 1 , Fernando Escobedo 2 , Ulrich Wiesner 1 Show Abstract
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States
Bottom-up type assemblies of amphiphilic block copolymers (BCPs) with nanoparticles (NPs) have attracted much attention for the potentially superior properties of the resulting nanocomposite materials for various applications such as electronics, optics, batteries, solar cells, and fuel cells. The use of a BCP as a structure directing agent enables spatial control of the BCP and NP components on the nanometer length scale. However, limited understanding of the underlying physics has hampered progress in this area. Reliable prediction of structure and quantitative analysis of properties by theoretical and simulation approaches may provide helpful insights to key experimental design criteria. In this work, we study BCP/NP self-assembly using a combination of self-consistent field theory (SCFT) and density functional theory (DFT). Long-range Coulomb and hard sphere interactions between NPs were implemented. We found that long-range Coulomb interactions lead NPs to form an ordered lattice within the microphase separated BCP nanostructures. Furthermore, we found that directed ABC tri-BCP assemblies with ligand-stabilized NPs can lead to a chiral NP network structure.
10:00 AM - **JJ1.3
Organic-inorganic Hybrid Copolymers Derived from Silsesquioxane or Carborane Building Blocks.
Edward Coughlin 1 Show Abstract
1 Polymer Science, Univ. of Massachusetts, Amherst, Massachusetts, United States
To explore competitive, or cooperative, effects novel organic-inorganic hybrid copolymers are being prepared and studied. The use of polyhedral oligomeric silsesquioxanes (POSS), a molecularly precise isotropic comonomer, is being utilized to take advantage of the inherent size scale of these particles, average diameters of 1-2 nm. The organic component selected for study in these hybrid systems are either semi-crystalline or amorphous polymers. The architectures of the hybrid copolymers range from random, to precise block copolymers, as well as telechelic and hemi-telechelic end-functionalized model compounds. The degree of POSS aggregation that occurs is found to be a function of thermal history, and processing conditions. Templating, or arresting, aggregation can be achieved using either competitive crystalline organic polymer scaffolds in the bulk, or rapid precipitation. The second inorganic comonomers for study has been constructed from icosahedral carboranes. Dicarbo-closo-¬decaboranes have been widely investigated for their thermal stability, chemical resistance, unique geometry, and the high cross-section for the capture of thermal neutrons. While carboranes have been widely incorporated into small molecules, metal complexes, and on a limited basis in polymer systems relatively little work exists relating their unique properties to systems with extended π-conjugation. Details of the syntheses, characterization and performance properties of both sets of these hybrid systems will be discussed
10:30 AM - JJ1.4
Directed Self-assembly with Density Multiplication of Cage Silsesquioxane-containing Block Copolymer Via Controlled Solvent Annealing.
Hiroshi Yoshida 1 , Yasuhiko Tada 1 2 , Yoshihito Ishida 3 , Tomoyasu Hirai 3 , Joan Bosworth 4 , Elizabeth Dobisz 4 , Ricardo Ruiz 4 , Teruaki Hayakawa 3 , Mikihito Takenaka 2 , Hirokazu Hasegawa 2 Show Abstract
1 Materials Reserach Laboratory, Hitachi Ltd., Hitachi Japan, 2 Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto Japan, 3 Department of Organic and Polymeric Materials, Tokyo Institute of Technology, Tokyo Japan, 4 San Jose Research Center, Hitachi Global Storage Technologies, San Jose, California, United States
Directed self-assembly of block copolymers (BCP) stands out as a promising alternative to overcome limitation in conventional lithographic techniques. Extensive work has shown that thermally self-assembled PS-block-PMMA may be aligned to lithographically defined chemical template with density multiplication [1,2]. However, the minimum dimension which can be attained by PS-b-PMMA is limited by its weak segregation power. Here we report density multiplication of chemically patterned template employing a strongly segregating polyhedral oligomeric silsesquioxane (POSS) containing block copolymer for extending the technique to smaller dimensions.The POSS-BCP, polymethylmethacrylate-b-polymethacrylate POSS (PMMA-b-PMAPOSS), and hydroxyl-terminated polymethacrylate POSS (PMAPOSS-OH) were synthesized by living anionic polymerization . Chemical template was prepared by pattering PMAPOSS-OH layer grafted on Si wafer by electron beam lithography. PMMA-b-PMAPOSS which self-assembles into hexagonally closed packed (hcp) array of dots with lattice spacing d=13nm was spin coated on the chemical template with doubled hcp lattice spacing d=26nm, and annealed under controlled CS2 atmosphere. By tuning the swell ratio of PMMA-b-PMAPOSS during annealing, an ordered array of dots with d=13nm, which corresponds to 3.5Tbit/in2, was obtained by interpolating dots in between the chemical template pattern and thus multiplying pattern density of the chemical template in a factor of 4.PMMA-b-PMAPOSS can potentially self-assemble into ordered domains with sub 10nm lattice spacing. The developed process therefore will provide a promising method for extending lithographical capability to very small dimensions for applications, including bit patterned media for next generation hard disk drives . R. Ruiz et al., Science 321, 936 (2008). Y. Tada et al., Polymer 50, 4250 (2009). T. Hirai et al., Macromolecules, 41, 4558 (2008). Authors acknowledge Prof. Padma Gopalan, University of Wisconsin-Madison, for supporting the synthesis of PMMA-b-PMAPOSS. This work was supported by New Energy and Industrial Technology Development Organization, Japan.
10:45 AM - JJ1.5
The Origins of Buckle Formation in Vapor Deposited Oxides on Polymers.
Michelle Casper 1 , Ying Liu 2 , Michael Dickey 2 , Kirill Efimenko 2 , Jan Genzer 2 , Jon-Paul Maria 1 Show Abstract
1 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 2 Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States
Electronic and photonic materials with periodically patterned micro- and nanostructures are of increasing and substantial importance . Consequent to this interest, spontaneous surface buckling has been transformed from a nuisance associated with hard and soft multilayers to a naturally occurring and attractive opportunity for producing hierarchically corrugated surfaces with intrinsic functionality. We investigate the origins of buckling instabilities in the indium tin oxide (ITO) – polydimethylsiloxane (PDMS) multilayer system and explore strategies for controlling the morphology with the potential for reversibility and tunability. The parameters investigated include deposition pressure, substrate temperature, strain, and energetic bombardment. We first identify the processing window that results in buckling during both radio frequency (RF) and direct current (DC) magnetron sputtering of ITO on thin film and bulk PDMS. Above a threshold deposition pressure, an unbuckled and cracked topography is observed, while below this pressure, a randomly oriented, wrinkled topography exists. Deposition onto heated PDMS results in two superimposed generations of buckles, each with its own characteristic wavelength, λ. Because these generations experience different dependencies on preparation conditions, this suggests different strain mechanisms, i.e., built-in and thermal expansion mismatch induced strain for the smaller and larger generations respectively. Next, we discuss the influence of internal stress accumulation during deposition on buckling by exploring ITO deposition on polystyrene (PS) films on Si. The samples were imaged as a function of temperature by hot stage microscopy to monitor the onset of buckling. In contrast to the PDMS system, buckling is not observed in PS multilayers until a post-deposition heating step above the Tg of PS is performed. In both cases, one generation of buckles occurs at temperatures above Tg and can be attributed to the relaxation of differential thermal expansion strain. For comparison to PDMS multilayers, ITO can be deposited on PS at T>Tg, and under conditions of internal stress accumulation two buckle generations are found. Collectively these observations allow us to identify the origins of stress generation, and thus buckle formation in multilayer structures. Thermal expansion mismatch, as reported by previous authors, is an important contributor, but stress effects can provide a similar influence.
11:30 AM - JJ1.6
Template-free Formation of Non-hexagonal Close Packing Regular Surface Structures Based on Self-assembly of Monodispersed Polymeric Nanoparticles.
Jun Yuan 1 2 , Ting Zhang 2 , Xinlin Tuo 3 , Jun Qian 4 Show Abstract
1 Department of Physics, University of York, York United Kingdom, 2 Beijing National Centre for Electron Microscopy, Tsinghua University, Beijing China, 3 Department of Chemical Engineering, Tsinghua University, Beijing China, 4 Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, Illinois, United States
Regular patterned surface structures are vital for many applications such as photonic or plasmonic devices or templates for preparation of other materials as well as nanosphere lithography. Preparation of such nanostructured surfaces is most efficiently carried out by using self-assembly of monodispersied nanoparticles. However, hexagonal close packing structure is most common result while many applications would benefit from a facile method of producing non-close-packing regular structure. Here we report a template-free approach to the formation of millimeter-sized films of (100) (square) facing face-cantered crystalline films (FCC) of colloidal nanoparticles by self-assembly on silicon substrates . We have shown that the formation of these pseudo-square packing surface patterns is related to the shape of the meniscus at the edges of the substrate, where the particles may suffer additional shear force and higher evaporation. Using this understanding, we can influence that the location and size of these nanoparticles thin films with pseudo-square surface arrangement. Using such approach to self-assemble polystyrene-methacrylic core-shell nanospheres into colloidal crystal films with square-like surface arrangement, we can not only demonstrate distinct optical response due to the surface square arrangement, but we can also transform these colloidal films into ordered pore structures by a simple toluene treatment . By detailed analysis, we have demonstrated the importance of local pseudo-square symmetry and compactness of the nanospheres assembly in determining the nature of resulting multiscale ordered pore structures due to selective fusion and dissolution of styrene-rich polymeric components.  T. Zhang, X. L. You and J. Yuan (2009) Langmuir, 25(2), pp 820-824 T. Zhang, J. Qian, X. L. Tuo and J Yuan (2010) Langmuir, 26(5), pp3690-3694
11:45 AM - JJ1.7
Electrophoretically Enhanced Fluidic Assembly of Nanoparticles.
Asli Sirman 1 , Cihan Yilmaz 1 , Jun Huang 1 , Sivasubramanian Somu 1 , Ahmed Busnaina 1 Show Abstract
1 , NSF Nanoscale Science and Engineering Center for High-rate Nanomanufacturing (CHN), Boston, Massachusetts, United States
Nanoparticles have generated much interest due to their potential use in devices requiring nanoscale features. Nanoparticles can serve as Raman spectroscopy substrates, photonic crystals, advanced batteries, biosensors and many other applications. The realization of commercial applications, however, depends on the development of rapid and precise assembly placement of nanoparticles. Fluidic directed self-assembly is one approach to achieving a precise assembly on the surfaces. In fluidic assembly, interfacial capillary forces at the liquid-air interface are used to precisely assemble nanoparticles into topographical geometries. However, the assembly duration is long due to the slow particle migration in the suspension toward the substrate (limited by diffusion). Here, we introduce an enhanced fluidic assembly technique for the rapid and precise directed assembly of nanoparticles onto insulating patterned surfaces. In this method, electrophoresis is used to overcome the diffusion limit encountered when using fluidic self assembly. To accomplish electrophoretically enhanced fluidic self-assembly of nanoparticles onto a dielectric film, a conductive film is utilized below the substrate (insulating film) to enable electrophoretic assembly. A DC electric field is applied between a patterned template and a counter electrode during assembly. The particles move towards the template under the influence of a DC electric field increasing the local particle concentration near the patterned template increase the speed of the assembly process by an order of magnitude or higher. Polystyrene Latex nanoparticles (50 nm) are assembled on a PMMA patterned 150 nm thick PECVD grown silicon oxide surface. A 150nm thick gold film, deposited underneath the oxide layer, is connected to the counter electrode providing the required electric field during the assembly process. We have investigated the effect of particle concentration, pulling speed and oxide thickness on the assembly process. The results show that the magnitude of the applied voltage plays a crucial role in achieving precise assembly at high pulling speed. For example, complete assembly using fluidic assembly can only be conducted speeds of 0.5mm/min or lower. However, when electrophoretically enhanced fluidic assembly is used, complete particle assembly can be achieved at speed of 3mm/min using at 3V. The results also indicate that using an electric field the time involved in fluidic assembly process can be reduced from hours to minutes. The results show that this method can yield a fast and high throughput assembly techniques enabling scalable particle assembly process for high-rate manufacturing of nanoscale devices.
12:00 PM - **JJ1.8
Liquid Crystalline Block Copolymer Template Films for Highly Ordered Nanostructured Materials.
Tomokazu Iyoda 1 , Motonori Komura 1 Show Abstract
1 Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
Microphase-separated nanostructures in block copolymers have fascinated one to understand the correlation between their ordered structures and the polymer structures so far, and now a new wave is surging on them as the self-assembled nanostructures leading to industrial use as the coming engineered plastics. Emphasis should be placed on both high reproducibility and mass production of these ordered nanostructures through self-assembling nanofabrication processes, expected as one of the powerful counterparts of the top-down-type nanofabrication such as lithography and beam processing.We have developed a series of PEO - liquid crystalline (LC) block copolymers which consist of poly(ethylene oxide) (PEO) and polymethacrylate bearing azobenzene mesogen in the side chain and have fabricated hexagonally arranged and normally aligned PEO nanocylinder domain structures in their thin films. Recently, we have prepared more than 100 kinds of the block copolymers with a variety of polymerization degrees of both blocks and mesogens and fabricated their meter-size area thin films on a roll-type PET film substrate by continuous coating with a microgravure. This success satisfies the above requirements applicable to industrial use and also guarantees their high regularity as reliable nanotemplates for structural transcription to and hybridization with various materials such as metal, semiconductors, and so on. One of the topics is to fabricate well-arranged metal nanoparticles arrays by using the nanocylinder structured template films. Both size and periodicity of the nanoparticles array can be controlled independently by choosing appropriate templates, which has never been achieved so far and can be applied for plasmonics engineering. In this talk, our recent results on multi-lateral structural analyses and several topics on transcription and hybridization will be introduced, together with our advanced polymer designs such as photocrosslinkable nanostructured films and region-specific single molecular modification on the micro-phase-separated nanostructures.
12:30 PM - JJ1.9
Dynamic Ordering of Attractive Monolayer Colloidal Crystals.
Kwan Wee Tan 1 , Yaw Koon Koh 2 , Yet-Ming Chiang 3 , Chee Cheong Wong 4 Show Abstract
1 Department of Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 2 , DSO National Laboratories, Singapore Singapore, 3 Department of Materials Science & Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 School of Materials Science & Engineering, Nanyang Technological University, Singapore Singapore
Ionic colloidal crystals, analogue of atomic ionic compounds and stabilized by long-range electrostatic attractions, have the potential to result in a wide diversity of nanostructures for novel photonic and phononic applications. However, electrostatic attractive interactions often result in irreversible coagulations and disorders between the oppositely-charged colloids and substrates. Here we demonstrate particle mobility can be tuned to form well-ordered colloidal crystals using the vertical deposition method even in the presence of electrostatic attractions. We control the ionic strength, colloidal concentration and solvent evaporation temperature to maximize mobility of positively-charged polystyrene particles to order into hexagonal close-packed monolayer colloidal crystals on bare negative glass surfaces. On the same note, the optimization of particulate mobility also allows the crystallinity enhancement of binary two-dimensional superlattices using oppositely-charged colloids grown layer-by-layer.
12:45 PM - JJ1.10
Heterogeneous Hydrothermal Reactions: A New Approach to Self Organized Core-Shell Hybrid Nanostructures.
David Munoz-Rojas 2 1 , Judith Oro-Sole 3 , Pedro Gomez-Romero 2 Show Abstract
2 , CIN2, Barcelona Spain, 1 , University of Cambridge, Cambridge United Kingdom, 3 , ICMAB-CSIC, Barcelona Spain
In the last years there has been a tremendous increase in the number of works involving the synthesis of nanomaterials, an in particular, of tailored nanostructures. The ability to control the final size and shape of such structures is meant to be the cornerstone upon which a new technological revolution is expected to take place. It is therefore a major necessity to fully understand the various processes involved on the nucleation and growth of nanomaterials if we are to achieve such technological breakthrough. Apart from the properties showed by materials at the nanoscale, our incursions in the nanoworld have allowed us to gain knowledge on a fundamental basis on such processes. A clear example is the discovery of Oriented Attachment mechanism,  as complementary to the traditional Ostwald ripening mechanism for crystal growth.  From the many studies so far performed it is well known that additives and synthetic conditions play a key role on the final structure. Also, and in addition to the peculiar properties associated to nanosized materials, novel properties and functionalities can be achieved by surface modification and combination of different materials. This has yielded a huge amount of mixed and hybrid nanostructures with novel properties.In our group we are exploring new approaches to the synthesis of silver-polypyrrole hybrid nanomaterials. As a result we have developed a simple procedure that yields Ag@Ppy core shell nanostructures. The synthesis involves the use of a suspension of Ag2O in an aqueous Py solution in the absence of any capping agent as PVP or PVA. The hydrothermal treatment of the suspension at temperatures between 120 and 150 C yields the spontaneous formation of novel tortuous Ag@Ppy nanostructures, which have been dubbed “nanosnakes” after their peculiar shapes, which form through self-assembly. Amazingly, the silver cores in these core-shell nanostructures present a high degree of crystallographic coherence in spite of their irregular shapes. In the present work, the experimental conditions for the synthesis of Ag@Ppy nanosnakes, their characterization and a discussion of the formation mechanism will be presented. The shape evolution of such structures and a proposed novel mechanism for crystal growth will also be discussed.[4,5] Finally, the extension of our method to other metals will be explored.1.- a) J. F. Banfield et al., Science 2000, 289, 751. b) R. L. Penn et al., Science 1998, 281, 969.2.- W. Ostwald, Lehrbruck der Allgemeinen Chemie; Vol. 2, Part 1. Leipzig, Germany, 1896.3.- D. Muñoz-Rojas, J. Oró-Solé, O. Ayyad, P. Gómez-Romero, Small 2008, 4, 1301.4.- D. Muñoz-Rojas, J. Oró-Solé, P. Gómez-Romero, J. Phys. Chem. C 2008, 112, 20312.5.- D. Muñoz-Rojas, J. Oró-Solé, P. Gómez-Romero, Chemical Commun. 2009, 5913.
JJ2: Supramolecular Assembly of Hybrid Materials II
Tuesday PM, November 30, 2010
Independence W (Sheraton)
3:00 PM - JJ2.1
Controlling Hierarchical Self-assembly of Polymer Bristles by Manipulating Meniscus Movement.
Sung Kang 1 , Ning Wu 1 , Joanna Aizenberg 1 2 3 Show Abstract
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Chemistry and Chemical Biology , Harvard University, Cambridge, Massachusetts, United States, 3 Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States
Evaporation-induced self-organization provides a simple way of assembling ordered and complex structures with different length scales. Previously, by combining top-down and bottom-up approaches, we have demonstrated hierarchical helical patterns of polymer bristles through self-assembly . In this process, controlling nucleation and propagation of the assembled clusters is important for tuning the size and pattern of the resulting assembly. As next steps, we have used various approaches to manipulate the formation and movement of the meniscus for better control of assembly process. In particular, we utilize confined geometries for directing the solvent evaporation and patterning the meniscus movement. We have observed a significant (~50 fold) improvement in the uniformity of the assembled features over large areas. In addition, we have produced intriguingly complex patterns with tunable periodicity and chirality. We will report our work on real-time imaging of the assembly process and mechanistic models for the observed pattern formation. This study enhances our understanding of the self-assembly of polymeric materials for building hierarchical structures and provides a simple way of fabricating complex ordered structures. B. Pokroy, S. H. Kang, L. Mahadevan, and J. Aizenberg, Science 323, 237 (2009).
3:15 PM - JJ2.2
Assembly of Nanoparticles from Bioactive Peptides and Chitosan.
Bing Hu 1 Show Abstract
1 Food Science, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, United States
Assembly of nanoparticles from bioactive peptides, caseinophosphopeptides (CPPs) and chitosan (CS) at physiological conditions and various CS/CPPs mass ratios have been systematically studied using a combination of liquid chromatography-tandem mass spectrometry (LC-MS-MS), turbidimetric titration, dynamic light scattering (DLS), electrophoretic mobility (zeta-potential), transmission electron microscopy (TEM), and florescence spectroscopy. Peptides with different amount of clusters of phosphorylated seryl residues have been prepared and identified using LC-MS-MS, which incorporated with CS forming nanoparticles. At low salt concentration, an increase of CS/CPP mass ratio shifted the critical pHφ1, which designated the formation of CS/CPP nanocomplexes, and pHmax, which represented the neutralization of positive and negative charge to higher pH values. The peptide-polymer binding mechanism and the binding constant were analyzed according to the results of DLS, electrophoretic mobility, TEM and florescence spectroscopy. First, negatively charged CPPs interacted with the positively charged CS to form intrapolymer nanocomplexes saturated with CPPs (CPPNP). Then, the negatively charged CPPNP was bridged by added positively charged CS. Finally, novel nano-scaled spherical brushes were formed as additional CS molecule absorbed back to and bound the CPPNP with the number of binding polymers = 1. The binding between the peptides and chitosan was mainly driven by electrostatic and hydrophobic interactions and the polymer-CPPNP binding constant was K=5.4*104 M-1 . Phosphorylated groups and Tryptophan (Tpr) in the CPPs might be the dominant sites for interaction with –NH3+ on the CS molecular chain.
3:30 PM - JJ2.3
Stimuli-responsive Self-assembly of Bionanomaterials toward Reconfigurable Devices.
Yoshiaki Maeda 1 2 , Prerna Kaur 1 , Hiroshi Matsui 1 Show Abstract
1 Department of Chemistry and Biochemistry, City University of New York, Hunter College, New York, New York, United States, 2 Department of Biotechnology, Tokyo University of Agriculture and Technology, Koganei, Tokyo, Japan
Stimuli-responsive bionanomaterials have been extensively applied to delivery systems, however recently they are indentified to have a potential to be useful in reconfigurable assemblies in the applications and microelectronics, sensors, and optoelectronics. Our strategy is to design smart building blocks that can response to various stimuli (pH, temperature, light or small molecules) and their attachment and detachment with specific substrates are controlled by molecular recognition, dependent on the stimuli. In this study, we constructed two kinds of stimuli-responsive biomaterials and applied them toward development of reconfigurable devices. One is the reconfigurable system controlled by the interaction between proteins and small molecular ligands. Magnetotactic bacteria synthesize intercellular magnetic nanoparticles, and functional protein can be displayed on the surface of magnetic nanoparticles using gene fusion techniques. Here two protein tags, His6 tag and glutathione S-transferase (GST) tag, were displayed in tandem to play key roles for the reconfigulation. Magnetic nanoparticles displaying His6 tag and GST tag could be attached on the silicon wafer modified with nickel-nitrilotriacetic acid (Ni-NTA) and glutathione respectively. These nanoparticles could be detached from the surfaces by incubating excess imidazole to break the His6 tag –NTA interaction or excess glutathione to break the GST tag-glutathione interaction. This interaction switch could realize the reconfiguration of magnetic nanoparticles on ligand-immobilized surfaces. Light-induced self-assembly (LISA) has potential to be a simpler and more rapid system in the stimuli-responsive smart devices. We genetically developed the building block for the LISA system, a collagen-like triple helix displaying azobenzene-binding peptide (Z877). Azobenzene converts its conformation by UV/Vis irradiation (UV=cis-azobenzene Vis=Trans-azobenzene). Since azobenzene-binding peptide (WPTPPNP) has high affinity toward cis-azobenzene specifically, the photoisomerization could turn on and off the interaction for the switching. After UV irradiation to azobenzene-immobilized wafers at dark room to make cis-rich azobenzene surface, Z877 peptides could bind the substrate due to the high affinity to cis-azobenzene detected by AFM. In contrast few binding was observed on the trans-azobenzene wafer, which was not irradiated by UV. Finally, we applied this LISA system to 3D assembly of gold nanoparticles and Z877 peptide. Recently we discovered that Au NPs can be assembled into 3D superlattices in peptide frames in precise NP arrangement in a large scale production, and here we could reversibly assemble and disassemble the 3D hybrid crystals by conjugating p-aminoazobenzene on NPs after the application of the LISA modulation.
3:45 PM - JJ2.4
Nanomechanical Stimulus by Atomic Force Microscopy Accelerated the Self-assembling Process of Peptide Based Nanofiber.
Jonathan Chang 1 , Xiu-Feng Peng 3 , Joseph Cappello 4 , Hamidreza Ghandehari 2 , Joonil Seog 1 Show Abstract
1 Materials Science and Engineering & Bioengineering, University of Maryland, College Park, Maryland, United States, 3 Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 4 , Protein Polymer Technologies, Inc., San Diego, California, United States, 2 Pharmaceutics and Pharmaceutical Chemistry and Bioengineering, University of Utah, Salt Lake City, Utah, United States
Many synthetic and natural peptides are known to self-assemble to form various nanostructures such as nanofibers, hollow tubes, or ring-like structures. Environmental conditions such as salt concentration, pH, temperature, protein content, and surface characteristics influence intermolecular interactions, hence the process of the self-assembly. Here we studied self-assembly of a genetically engineered protein polymer composed of silk-like and elastin-like repeats on a mica surface. Silk-elastinlike protein polymers (SELPs) consist of tandem repeats of Gly-Ala-Gly-Ala-Gly-Ser from Bombyx mori (silkworm) and Gly-Val-Gly-Val-Pro from mammalian elastin. At a very low polymer concentration, SELPs readily self-assembled into nanofibrous structures on a mica surface. Examination using atomic force microscopy (AFM) and dynamic light scattering techniques showed that SELPs self-assembled into nanofibers only in the presence of the mica surface but not in the bulk state. Ionic strength had a significant influence on nanofiber growth, indicating the importance of electrostatic interactions between the polymer and the mica surface. Interestingly, SELP with a high content of silk repeat showed very low density of nanofiber initially but the density slowly increased without any addition of SELP from the bulk phase, indicating that the nanofiber grew by self-assembling pre-existing SELP on a mica surface. Furthermore, the rate of fiber growth was dramatically accelerated by mechanical stimulus by AFM. The direction of the newly formed nanofibers was dependent on AFM scanning direction, suggesting that this system is potentially applicable to create nanofiber patterned surface by nanomechanical stimulus.
4:30 PM - JJ2.5
Poly(amino acid)s-mediated Synthesis of Spatially Organized Pt Nanoparticles.
Jae Hyun Jeong 1 , John Haan 1 , Chaenyung Cha 1 , Deryn Chu 2 , Hyunjoon Kong 1 Show Abstract
1 Chemical and Biomolecular, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 , U.S. Army Research Laboratory, Adelphi, Maryland, United States
Nanometer-sized noble metal particles are being increasingly studied for use in various applications including photochemistry, electrochemistry, optics, and catalysis. Recently, extensive efforts have been made to improve nanoparticle dispersion to enhance its performance using various surfactants, dendrimers and polyelectrolytes which can tune colloidal interactions. However, it is still challenging to establish a technology in which spatial organization of metal nanoparticles is finely controlled at varied length scales. Here we present that in situ sol-gel polymerization of metal precursors incorporated into self-assembling poly(amino acid) nanostructure would generate metal nanoparticles with regular spacing at the nanometer scale. This hypothesis was examined using poly(amino acid)s substituted with alkyl chains to form various morphologies from a spherical micelle to a bilayer structure. Platinum precursors (K2PtCl4) were mixed with alkyl-substituted poly(amino acid)s solution followed by reduction to activate sol-gel polymerization to form Pt particles. We discovered that particle size and spacing were dependent of the degree of substitution (DS) of alkyl chains. Specifically, alkyl-substituted poly(amino acid)s with DS of 5 % were assembled into a vesicle with an average diameter of 100 nm, and also presented Pt nanoparticles with diameter of 2 to 5 nm exclusively within a bilayer of the vesicle. Furthermore, the resulting Pt nanoparticles showed a significantly enhanced electro-catalytic activity as compared with Pt particles polymerized via bulk sol-gel polymerization. Taken together, the results of this study demonstrated that the size and spacing of metallic particle can be controlled using a self-assembling polymeric template. The resulting particles present strong potentials to significantly improve performance of a variety of energy storage and generation systems.
4:45 PM - JJ2.6
Biomimetic Assembly of Nanoparticles Using Collagen Peptide Framework.
Prerna Kaur 1 , Yoshiaki Maeda 1 , Hiroshi Matsui 1 Show Abstract
1 Chemistry, Hunter College, New York, New York, United States
Applying biomimetic strategy to control the self-assembly of complex three-dimensional (3D) architectures could lead to the development of complex device configurations. In order to achieve high yields of ordered macroscopic 3D material, we exploited the specificity and robustness of peptides to design a simple and rapid fabrication protocol that result in high yields of 3D crystals.In this study, we report self-assembly of peptides and ligand-functionalized nanoparticle (NP) into micron scale 3D cube-shaped crystals, creating a physical framework for the proposed biomimetic assembly strategy. Taking advantage of the lateral assembly and robust scaffolding nature of collagen, we designed genetically modified collagen like triple helix peptides as nanowire building blocks that can specifically interact with gold nanoparticles functionalized with streptavidin. The design feature of this triple helix includes a segment of alpha 1 chain of type 1 collagen that displays 15 amino acid based Biotin Acceptor Peptide (BAP)that exhibits effective bio recognition sequence that in vivo biotinylates at specific lysine residue at the N-terminus. Using the intrinsic ability of collagen to self associate, we used streptavidin-functionalized gold nanoparticles that can join the peptide nanowires through the streptavidin-biotin interaction to create cubic unit cells with peptide nanowires forming the framework to align NPs. The high yields that resulted from this simple assembly at various scales predict the ability to create an extensive latticework of cubic microcrystals. The NPs are ordered in a long range with the uniform orientation with high yields of 3D materials in controlled shapes, dependent on the geometry of the NP-peptide lattice. The robust large-scale assembly nature of peptides in ordered structures could be advantageous to generate macroscopic building blocks that still preserve functional nanometric domains in the structure. Altering the size ratio between triple helix peptides and NPs and/or the number of ligands on NPs can alter the final crystalline structure. The ability to synthesize protein based functional hybrid material with peptide assembly and nanoparticles building blocks concurrently provides the functionality derived from both the inorganic fragment for electrical conductivity and the protein fragment for bio catalysis and bio recognition demonstrating the feasibility of using structurally stable protein for the designing novel materials.
5:00 PM - **JJ2.7
Thiol-ene Click Chemistries for the Formation of Nanoparticles and Encapsulation of Bioactive Cargo.
Eva Harth 1 , Alice Van der Ende 1 , Jameson Harrell 1 , Jared Katz 1 Show Abstract
1 Chemistry, Vanderbilt University, Nashville , Tennessee, United States
We report the successful systematic preparation of biodegradable nanoparticles in a variety of distinct nanoscopic size dimensions using the traditional alkyne-azide click chemistry and the thiol-ene click reaction by covalently cross-linking alkyne or allyl functionalized linear polyesters with bisazides or dithiols respectively. Characterization of the particles by dynamic light scattering (DLS), and transmission electron microscopy (TEM) proves that the presented cross-linking chemistries provide novel processes for forming nanoparticles. The mild reaction conditions allow for the encapsulation of bioactive cargo such as peptides and oligonucleotides during nanoparticle formation in organic and hydrophilic media.
5:30 PM - JJ2.8
Examining the Properties of Suspensions and Self Suspended Fluids Based on Cubic Cobalt Oxide Nanoparticles.
Wanda Jones 1 , Lynden Archer 1 , Tamara Smith 2 Show Abstract
1 Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York, United States, 2 Chemical Engineering, Tuskegee University, Tuskegee, Alabama, United States
Metal oxide nanoparticles have generated significant scientific and commercial interest in the last decade as platforms for controlling and studying materials chemistry and physics. Cobalt oxide nanostructures, especially the Co3O4 phase, are important materials used for a broad range of electrochemical, magnetic and catalytic applications. Several previous studies have considered synthesis of cobalt oxide nanoparticles and their end-use applications. Fundamental studies of processability and stability of Co3O4 nanostructures are less common, but arguably as important for full exploitation of these materials. In this study we focus on two classes of cube-shaped Co3O4 nanoparticle suspensions. In one group the suspensions are created by dispersing particles in an oligomeric polyethylene oxide liquid carrying predetermined amounts of polyvinylpyrrolidone (PVP) as a capping agent. In the second group, the particles are densely grafted by covalent attachment of an oligo polyethylene oxide (PEG) corona, which also forms the suspending medium. We report on the effect of coupling between the suspending medium and suspended particles on quiescent and shear-induced structural transitions in these suspensions. PEG/PVP-based suspensions show Newtonian behavior under the conditions of this work with shear viscosity as a strong function of particle concentration. Self-suspended fluids exhibit various glassy behaviors as a function of particle concentration.
5:45 PM - JJ2.9
Self-asembling Functionalized Amino Acids into Unusual Shapes.
Justin Barone 1 , Naresh Budhavaram 1 , Kate Harvey 1 Show Abstract
1 Biological Systems Engineering, Virginia Tech, Blacksburg, Virginia, United States
Multi-component small molecule systems that are amphiphilic or that can hydrogen bond end-to-end or side-to- side have been shown to self-assemble into a variety of shapes including fibers, rods, sheets, plates, spheres, and tubes. Recently, we have identified a simple route to self-assemble the same shapes from simple one-component systems. The structures form by attaching ethyl vinyl sulfone (EVS) to amino acids in water at pH 9 and room temperature. Choice of amino acid and amount of EVS substitution determines the final shape. Functionalized amino acids spontaneously form structures like fibers, spheres, tubes, and donuts when dried from aqueous solution.
Padma Gopalan University of Wisconsin-Madison
Qing Wang The Pennsylvania State University
Hilmar Koerner U. S. Air Force Research Lab/RXBN
Dhandapani Venkatraman University of Massachusetts Amherst
Teruaki Hayakawa Tokyo Institute of Technology
JJ5: Poster Session
Wednesday PM, December 01, 2010
Exhibition Hall D (Hynes)
JJ3: Synthesis and Self-assembly of Block Copolymer Materials
Wednesday PM, December 01, 2010
Independence W (Sheraton)
9:45 AM - JJ3.2
Block Copolymer Nanotiled Electrode for Conducting Polymer Nanostructures.
Hideaki Komiyama 1 , Motonori Komura 1 , Keiji Nagai 1 , Tomokazu Iyoda 1 , Kaori Ito 1 2 Show Abstract
1 Chem. Res. Lab., Tokyo Institute of Technology, Yokohama, Kanagawa, Japan, 2 , JST-PRESTO, Kawaguchi, Saitama, Japan
Polymerization for conducting polymers inside the pores of track-etched membrane and anodic porous alumina membrane as a template has been demonstrated to give the nanostructured morphology and tune the properties of the resulting nanostructured conducting polymers due to alignment of the π-conjugated main chains. Electropolymerization for conducting polymers is a well-known technique for providing the thin film and easily controlling the deposited amount. Herein, we demonstrate the electropolymerizaiton for conducting polypyrrole (PPy) using the PEOm-b-PMA(Az)n diblock copolymer thin film as a template, which was developed in our laboratory.1 The PEO nanocylinders of which the diameter and the periodicity are size-tunable with narrow distribution are formed with perpendicular orientation to the substrate in the thin film by microphase-separation. The cylindrical domains are not physical pores unlike the track-etched membranes and anodic porous alumina manbrane. The nanocylinders are filled with PEO in over-cooled liquid state, which exclusively dissolves polar substances such as pyrrole here. The perpendicularly aligned PEO nanocylinder array on an electrode can work as electrochemical nano-scaled electrolytic medium.PEO114-b-PMA(Az)45-coated ITO electrode, Pt plate and Ag/AgCl were employed as working, counter and reference electrodes, respectively. Electropolymerization of pyrrole was performed under potentiostatic or galvanostatic condition. The template was taken off from the top surface by dissolution method with a mixed solution of toluene and acetone under spinning condition, called chemical etching here. AFM and FE-SEM observation gave hexagonal dot-pattern with dot diameter of 10 nm and the periodicity of 27 nm, corresponding to those of the PEO nanocylinder domains. The chemical etching clearly revealed the top edges of PPy nanowire array halfway growing through the PEO nanocylinders. When further electropolymerization was proceeded, the PPy nanowires grew over the template film and then the PPy film was covered over the surface of the template. The length of nanowires was controlled by the film thickness of the template and the amount of passed charge. We have successfully obtained the PPy nanowires up to 1.4 μm in height. We have also fabricated the PPy nanowire array with the size of (diameter-nm, periodicity-nm) = (7, 13) and (17, 35) by using the PEO40-b-PMA(Az)17 and PEO272-b-PMA(Az)94 template, respectively, by adopting various block copolymer templates with different PEO size. The nonporous PEOm-b-PMA(Az)n thin film composed of two kinds of microdomains with chemical contrast can be expected as a nanotiled template. Electropolymerization could be carried out in not only the nanocylindrical microdomains but also in the matrix domains by solubility of monomers, supporting electrolyte and solvent to the microdomains. T. Iyoda et al., Macromolecules 2002, 35, 3739
10:00 AM - **JJ3.3
Self-assembly of Block Copolymers and Applications to Semiconducting and Bioinspired Molecules.
Rachel Segalman 1 2 , Adrianne Rosales 1 2 , Victor Ho 1 2 , Ron Zuckermann 2 Show Abstract
1 Chemical Engineering, UC Berkeley, Berkeley, California, United States, 2 Materials Science Division, Lawrence Berkeley National Laboratories, Berkeley, California, United States
The ability to control nanoscale structure in functional systems such as semiconducting polymers for energy generation or biologically inspired polymers would enable new applications, but control over self-assembly in these systems presents new challenges. In particular, the thermodynamics of self-assembly in these systems is significantly altered from that of well-characterized classical block copolymers due to differences in chain topology and the liquid crystalline and/or crystalline interactions. We have studied both the fundamental self-assembly of molecules of unusual shapes as well as applied these principles to conjugated rod-like blocks for photovoltaic and light emitting devices and to bioinspired polymers with tunable molecular conformations. In both cases, we find that careful molecular design to moderate molecular interactions is essential in creating controllable systems. In particular, both sidechain substitution and sequence control can be used to control melting temperatures and liquid crystalline interactions in order to create a processing window in which self-assembly can occur. The role of intermolecular interactions as well as mechanisms for pattern control will also be discussed.
10:30 AM - JJ3.4
Multi-functional Smart Materials from Hierarchically Ordered Polymeric Systems.
Rajeswari Kasi 1 2 , Suk-kyun Ahn 2 , Yuxiang Zhou 1 , Prashant Deshmukh 1 , Rubinder Kaur Lakhman 2 , Nitin Sharma 1 , Victoria Briand 1 Show Abstract
1 Chemistry Department, University of Connecticut, Storrs, Connecticut, United States, 2 Polymer Program, University of Connecticut, Storrs, Connecticut, United States
Cholesterol can be used as a building block to prepare main-chain and side-chain liquid crystalline polymers (LCPs) in which the cholesteryl moieties self-assembles into different liquid crystalline (LC) mesophases. These LC mesophases include layered smetic A, C, nematic and cholesteric structures that can be tailored based on the composition of the polymer, presence of functional groups and polymer processing conditions. We wish to exploit the stimuli-responsive properties of these LCPs bearing side-chain cholesteryl moieties towards the creation of multi-functional smart materials. We have synthesized cholesterol bearing liquid crystalline homo-, random and block polymers with additional functional (or polar) groups, composition, and architecture. Our synthetic protocol has been used as a handle to tailor the thermal and morphological properties of these LCPs. We have investigated strategies to direct ordering and packing of meso- and nanostructures originating from these LCPs both in solid state and in solutions. These nanostructured polymers with and without inorganic nanoparticle additives have been used to create shape memory devices, actuators, and multi-stimuli responsive materials.
10:45 AM - JJ3.5
Surface Grafted Conjugated Polymers.
Joseph Peterson 1 , Sarav Jhaveri 1 , Kenneth Carter 1 Show Abstract
1 Polymer Science & Engineering, University of Massachusetts-Amherst, Amherst, Massachusetts, United States
Surface tethered conjugated polymers have the potential to impact organic electronics by through precise control of interface structures, chain alignment, charge transport, and other properties. Brush structures may give access to well defined structures that are unattainable through traditional fabrication and patterning techiniques. Viable synthetic strategies are the first step towards the practical study and utilization of conjugated brush-type structures.Conjugated polymers were tethered by functionalizing surfaces with monomer-like functionality. Polyfluorene based polymers were tethered to inorganic surfaces such as silicon and quartz wafers as well as to natural fiber surfaces such as paper or cellulose. The surfaces displayed characteristic properties of the grafted polymers such as fluorescence emission, etc, and were stable to subsequent processing, unlike deposited thin films. The surface grafted polymers may have applications in light emitting devices, solar cells, and polymer batteries.
11:30 AM - JJ3.6
Block Copolymers for Idealized Morphologies in Organic Photovoltaic Active Layers.
Ioan Botiz 1 , Rafael Verduzco 2 , Seth Darling 1 Show Abstract
1 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 2 Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas, United States
By controlling the nanoscale morphology within organic photovoltaic active layers, there are opportunities to gain insights into structure-property relationships that underlie device performance. Block copolymers, which naturally self-assemble into periodic ordered nanostructures, can be utilized in diverse ways to control morphology, ranging from active layers to structure directors to a combination of these methodologies. We present two such approaches, based on rod-rod and rod-coil block copolymer architectures, respectively. Through structural and spectroscopic studies of ordered donor/acceptor systems, connections between the morphology and the optoelectronic properties are deciphered.
11:45 AM - JJ3.7
Facile Synthesis of Well-defined Coil-rod-coil Block Copolymers Containing Regioregular Poly(3-hexyl thiophene) by Anionic Coupling Reaction.
Hong Chul Moon 1 , Jin Kon Kim 1 Show Abstract
1 Chemical Engineering, POSTECH, Pohang, Kyung-buk, Korea (the Republic of)
We synthesized coil-rod-coil triblock copolymers composed of regioregular poly(3-hexyl thiopene) (P3HT) block via anionic coupling reaction. Two different coil blocks (poly(2-vinyl pyridine) (P2VP) and polyisoprene (PI)) were selected. P2VP-b-P3HT-b-P2VP copolymer was synthesized in a polar solvent of tetrahydrofuran, while PI-b-P3HT-b-PI copolymer was synthesized in a nonpolar solvent of benzene. For the synthesis of both block copolymers, the chain ends of the P3HT were capped by the aldehyde group. When the excess amount of the living P2VP (or PI) anions was used, all of aldehyde-capped P3HT were completely reacted with P2VP (or PI) anions, without leaving any P3HT homopolymer in the product. Neat block copolymers were separated from the crude product by column chromatography, resulting in well-defined sharp and narrow molecular distribution.
12:00 PM - **JJ3.8
Diblock Copoly(3-alkythiophene)s: Synthesis, Self-Assembly and Their Uses in Photovoltaic Cells.
Samson Jenekhe 1 2 , Guoqiang Ren 1 , Pei-Tzu Wu 1 , Raffaele Mezzenga 3 Show Abstract
1 Department of Chemical Engineering, University of Washington, Seattle, Washington, United States, 2 Department of Chemistry, University of Washington, Seattle, Washington, United States, 3 Department of Physics and Fribourg Center for Nanomaterials, Fribourg University, Fribourg Switzerland
Block conjugated copolymers are of growing interest in the fabrication of bulk heterojunction solar cells because of their intrinsic ability to form nanoscale domains by self-assembly. We have synthesized and investigated the solution-phase self-assembly, melt-phase phase behaviour, and optoelectronic properties of new all-conjugated diblock copoly(3-alkylthiophene)s. The morphology, charge transport, and photovoltaic properties of poly(3-butylthiophene)-b-poly(3-octylthiophene) (P3BT-b-P3OT) have been investigated as a function of block composition. Diblock copoly(3-alkylthiophene)s annealed above the homopolymer melt transitions (280 °C) were observed by small and wide angle X-ray scattering (SAXS and WAXS) to be microphase-separated into a lamellar structure with two crystalline domains. The microphase-separated domains were characterized by two distinct interlayer d-spacing values that are associated with the two different blocks respectively. In solution, the diblock copoly(3-alkylthiophene)s self-assembled into crystalline nanowires with widths of 14-16 nm and aspect ratios of up to 350-850. Bulk heterojunction solar cells comprising blends of P3BT-b-P3OT and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) were found to have power conversion efficiencies as high as 3.0%, which are substantially enhanced compared to those of the homopolymers made under similar conditions. Our results demonstrate that block conjugated copolymers offer a promising approach to advanced materials with tunable morphology and properties for the development of more efficient polymer solar cells.
12:30 PM - JJ3.9
Towards Optimum Morphology of Polymer Bulk Heterojunction Solar Cells.
Chetan Singh 1 , Michael Sommer 2 , Marcel Himmerlich 1 , Stefan Krischok 1 , Mukundan Thelakkat 3 , Harald Hoppe 1 Show Abstract
1 Institute of Physics, TU Ilmenau, Ilmenau Germany, 2 Department of Chemistry, University of Cambridge, Cambridge United Kingdom, 3 Applied Functional Polymers, University of Bayreuth, Bayreuth Germany
We present an approach for achieving optimum morphology in polymer solar cells utilising blend of self assembling donor-acceptor diblock copolymer (DCB) and homopolymer acceptor. In this way, we managed to control the linear rise in open circuit voltage (Voc) and short circuit current (Isc) in the solar cell structure with increasing acceptor content. In the investigated system, the donor and hole conductor was poly(3-hexylthiophene), P3HT, the acceptor and electron conductor was poly(perylene bisimide acrylate), PPerAcr. The improved performance for optimum morphology is attributed to reduced recombination of charge carriers at the cathode interface due to the surface segregation of the acceptor, as identified by atomic force microscopy and X-ray photoelectron spectroscopy measurements. In an effort to engineer the cathode interface, we were able to successfully control Voc at high values (~ 640 mV) by deliberately introducing an acceptor interlayer at the cathode interface.
12:45 PM - JJ3.10
Selenophene-Thiophene Block Copolymers.
Dwight Seferos 1 , Jon Hollinger 1 Show Abstract
1 , University of Toronto, Toronto, Ontario, Canada
Selenophene-thiophene block copolymers were synthesized and studied. The properties of these novel block copolymers are distinct from statistical copolymers prepared from the same monomers with a similar composition. Specifically, block copolymers exhibit broad and red-shifted absorbance features and phase separated nanoscale domains in the solid-state. Scanning transmission electron microscopy and topographic elemental mapping confirms that domains are either rich in selenophene or thiophene, indicating that the blocks of distinct heterocycles preferentially associate with one another in the solid-state. This preference is surprising given the chemical similarities between repeat units. The overall results demonstrate a form a phase separation that is controlled by elemental differences. As a result of phase separation and the ability to concurrently control optical properties, these novel conjugated block copolymers should find utility in a variety of studies and optoelectronics uses.
JJ4: Nanostructured Materials for Energy Related Applications
Wednesday PM, December 01, 2010
Independence W (Sheraton)
2:30 PM - JJ4.1
Porphyrin Nanoparticles: Diversity Enabled via Synthetic Manipulations.
Suk Joong Lee 1 Show Abstract
1 Chemistry, Korea University, Seoul Korea (the Republic of)
Over the past decades, the self-assembly approach has developed into a powerful technique for synthesis of nanostructures. Particularly, porphyrins have become one of the most attractive building blocks for self-assemblies because of the enormous potential that they possess in catalysis, photochemistry, sensing, and as optical devices has made them favorite building blocks in the emerging field of molecular materials. With attractive structural features such as large bulk, rigid planarity, and a highly conjugated framework that can be readily modified with a variety of functional groups, porphyrins can be assembled into supra- and super-structures in a relatively facile manner. Indeed, porphyrin building blocks have been used extensively in the construction of nano-, micro-, and macroscopic structures, including nanomaterials using π-π interactions, electrostatic interactions, and metal coordination with appropriate choice of substituents. However, examples of porphyrin based nano particles with different morphology are quite rare. We are particularly interested in the rational synthesis of porphyrin based unique nano particles showing a variety of morphology by the manipulation of secondary substituents (i.e., substituents that are not directly bonded to the porphyrin ring) to engender van der Waals interactions beyond the immediate porphyrin ring. In this presentation, we like to introduce synthesis and assemblies of nano-objects based on the substituents such as carboxylic acids and pyridines on 5 and 15 positions on porphyrin, and influence of secondary substituents in the process of nano-objects assemblies.
2:45 PM - JJ4.2
Fast and Efficient Spin Spray Layer-by-Layer Assembly of Polymer / Carbon Nanotube Hybrid Thin Films for Electrochemical Systems.
David Kohn 1 , Xiaokai Li 1 , Forrest Gittleson 1 , Mauricio Zurita-Gotor 3 , Jerzy Blawzdziewicz 2 , Andre Taylor 1 Show Abstract
1 Chemical Engineering, Yale University, New Haven, Connecticut, United States, 3 Ingenieria Aeroespacial y Mecanica de Fluidos, Universidad de Sevilla, Sevilla Spain, 2 Mechanical Engineering, Yale University, New Haven, Connecticut, United States
Layer-by-layer (LbL) assembly, an elegant bottom-up nanomanufacturing technique, has promising applications in fields as diverse as drug delivery, high-strength materials, and electrochemical systems including batteries, fuel cells and solar cells. The great potential of the technique is its ability to blend disparate materials into hierarchical, self-assembled nanocomposites. However, low throughput and material efficiency continue to make the process prohibitively expensive for industrial applications and hinder basic research. Spin spray LbL (SSLbL) addresses these problems by spraying polyelectrolyte solutions or nanocolloidal suspensions onto a spinning disc in rapid succession. Here we show that SSLbL with in-situ heating can achieve short cycle times (< 18 seconds / bilayer) and increase throughput and material efficiency of LbL for electrochemical applications.We used SSLbL to fabricate thin hybrid polymer/carbon nanotube (CNT) electrodes as a model system towards optimizing electrical conductivity. SSLbL assembled films achieved higher transmittance than traditional LbL films with similar conductivities. For instance, a 20 bilayer SSLbL film (16.3 kOhm / sq sheet resistance) transmitted 90% of light at 550nm while a 6 bilayer LbL film (16.9 kOhm / sq sheet resistance) transmitted 85%. Assembling a 20 bilayer SSLbL film requires 6 minutes, compared to a 6 bilayer LbL film, which requires ~ 4 hours. SSLbL’s thinner bilayers and high throughput allow fabrication and characterization of a large number of samples with tunable thickness and conductivity. We observed that conductivity per bilayer increased until saturation and, to explain this behavior, we developed a theoretical model in which junctions between CNT’s were designated to be the major source of sheet resistance. The composite was simulated as a stack of percolating CNT sheets separated by insulating polymer layers. We will show how this model enables optimization of the thin conductive films and provides guidance for further work on the design of nanostructured, high-performance battery electrodes  and fuel cell membrane electrode assemblies .  Lee, S. W.; Yabuuchi, N.; Gallant, B. M.; Chen, S.; Kim, B.-S.; Hammond, P. T.; Shao-Horn, Y. Nat Nano 2010, advance online publication.  Taylor, A. D.; Michel, M.; Sekol, R. C.; Kizuka, J. M.; Kotov, N. A.; Thompson, L. T. Advanced Functional Materials 2008, 18, (19), 3003-3009.
3:00 PM - **JJ4.3
Nanoscale Templating and Assembly in Dye-sensitized Solar Cells.
Michael Durstock 1 , Giorgio Bazzan 1 , James Deneault 2 , Tae-Sik Kang 2 , Barney Taylor 2 Show Abstract
1 , The Air Force Research Lab, Wright-Patterson AFB, Ohio, United States, 2 , UTC, Beavercreek, Ohio, United States
The development of low-cost, lightweight, and flexible energy harvesting devices are an enabling technology for many different solar power applications. The fabrication of highly efficient power conversion devices are highly dependent on the materials and device structures used to make up the active components. Two factors limiting the performance of organic and nanoparticle-hybrid solar cells are limited spectral response and restricted charge transport. These effects can result from poor light absorption, increased carrier recombination, low electronic charge carrier mobilities, or relatively random thin film morphologies. Our efforts to broaden the spectral response of dye-sensitized solar cells are based on developing a detailed understanding of the assembly of dye molecules on the surface of the mesoporous titania film. By utilizing an interfacial modification technique based on layer-by-layer assembly, nanoparticle surfaces can be functionalized with electronically active species and integrated into device structures. This technique is amenable to developing ‘energy cascade’ device architectures commonly utilized in photosynthetic organisms. Our efforts to develop a detailed understanding of this interfacial structure as well as approaches to fabricate multilayer assembled films for enhanced absorption will be described. In addition, our efforts to develop the materials and fabrication methodologies that result in highly ordered device structures to permit enhanced charge transport will be discussed. These include a nano-templating methodology based on porous anodic alumina in order to fabricate vertically aligned titania nanotubes of controllable shape and size. Structure-property correlations relating nanoscale morphology of the nanotubes to device performance will be discussed. In addition, we will highlight current barriers to improved performance and describe a number of specific approaches being investigated to address these issues.
3:30 PM - JJ4.4
Periodic Titania Nanostructures Using A Block Copolymer Templating Approach.
Devon Shipp 1 , Qin Lou 1 , Pavan Chinthamanipeta 1 Show Abstract
1 Chemistry, Clarkson University, Potsdam, New York, United States
For some time now it has been well recognized that phase separation within block copolymer thin films has significant potential in various fields. One such application is that these thin films can form templates with regular, periodic patterns which can be used to deposit or construct other functionality or features; the block copolymer can be later removed using various methods. Additionally, the development of well-ordered semi-conductor nanostructures, especially of titania (TiO2) for photovoltaic (PV) applications, is currently an area of intense interest. However, there are many barriers to overcome if well-ordered TiO2 nanostructures are to become widely applicable. One reason for the difficult production of well-ordered TiO2 nanostructures is the high reactivity of the crystalline surfaces.In this paper we report the preparation of high density arrays of titania nanostructures on silicon and indium tin oxide (ITO) glass substrates using polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer template and titanium(IV) bis(ammonium lactate) dihydroxide (TALH) as the TiO2 precursor. The procedure can exclusively involve solution processing and can be applied to a variety of substrates. The PS-b-P4VP block copolymer forms P4VP cylinders that orientate perpendicular to the substrate and it is these P4VP cylinders that are ultimately where the TiO2 are deposited. Various analytical methods, such as field emission scanning electron microscopy (FE-SEM) atomic force microscopy (AFM) and transmission electron microscopy (TEM), show that well-aligned arrays of titania nanostructures are produced and the block copolymer acts as a template for these nanostructures.
3:45 PM - JJ4.5
Semicrystalline Organometallic Block Copolymer Micelles with Symmetrically Substituted Poly(ferrocenylsilane) Compartments.
Felix Schacher 1 2 , Torben Gaedt 1 , Ian Manners 1 Show Abstract
1 School of Chemistry, University of Bristol, Bristol United Kingdom, 2 Institute of Organic and Macromolecular Chemistry, University of Jena, Jena Germany
The self-assembly of poly(ferrocenylsilane) (PFS) containing block copolymers in solution has bee