To better understand the physical and electronic properties of donor and acceptor-based structures used in organic electronic applications, a variety of oligothiophene and naphthalene diimide-based small conjugated molecules were designed, synthesized, and characterized. The materials were initially synthesized using oxidative copper-chloride coupling reactions, palladium-catalyzed amination reactions, Friedal-Crafts acylations, Negishi coupling reactions, and Stille coupling reactions. Once isolated, the physical properties of the compounds were characterized through a combination of X-ray crystal structure, thermogravimetric analysis, differential scanning calorimetry, UV-vis. absorption spectroscopy, cyclic voltammetry, and differential pulse voltammetry, along with comparison to quantum-chemical calculations. In some cases, the radical cations or radical anions were generated by chemical oxidation and analyzed by vis-NIR spectroscopy. Furthermore, the electronic properties of the materials were investigated through incorporation as solution-processed active layers in organic field-effect transistors. Multiple examples exhibited hole- and / or electron-transport properties with electron mobility values of up to 1.5 cm²V⁻¹s⁻¹, which is among the highest yet reported for an n-channel OFET based on a solution-processed small molecule.

Using block copolymers for large-area periodic structure fabrication is of great interest because of the potential for low fabrication costs and simplicity of the processing. The concept is that by selective inclusion of the nanoparticles into one of the blocks of a self-assembling copolymer, the nanoparticles are forced into a defined spatial arrangement determined by the phase morphology of the copolymer. Although copolymers can form well defined structures, they inherently have a 'polycrystalline' structure in the bulk, meaning that there is no long-range order of the domains. This thesis addresses both the effect of inclusion of the nanoparticles and the long range ordering of block copolymer domains. The first part of the thesis focuses on the study of the effect of nanoparticle inclusions on the phase morphology of the poly(styrene-butadiene) diblock and poly(styrene-butadiene-styrene) triblock copolymers. For gold inclusions, it was found that even at relatively low concentrations of inclusions (less than 1 wt./vol.%) the block copolymer phase morphology is altered from that of the native copolymer. By contrast to the block copolymer-gold system, no significant changes in bulk morphology is observed for similar fullerene concentrations. In the second part of the thesis, the evolution of the order in cylinder forming poly(styrene-butadiene-styrene) triblock copolymer thin films as a function of the type of solvent vapor, exposure time to the saturated vapors and substrate surface energy is discussed. Solvent vapors of dimethoxyethane, ethyl acetate and cyclohexanone were found to be the most effective for our polymer films. Solvent vapors differing in their selectivity towards the block copolymer domains have different kinetics of ordering which is explained in terms of the difference in the interaction of the solvent between the two different copolymer blocks.

As humanly engineered materials systems approach the atomic scale, top-down manufacturing approaches breakdown and following nature's example, bottom-up or self-assembly methods have the potential to emerge as the dominant paradigm. Synthesis of one-dimensional nanomaterials takes advantage of such self-assembly manufacturing techniques, but until now most efforts have relied on high temperature vapor phase schemes which are limited in scalability and compatibility with organic materials. The solution-phase approach is an attractive low temperature alternative to overcome these shortcomings. To this end, this thesis is a study of the rationale solution-phase synthesis of ZnO nanowires and applications in photovoltaics. The following thesis goals have been achieved: rationale synthesis of a single ZnO nanowire on a polymer substrate without seeding, design of a wafer-scale technique to control ZnO nanowire array density using layer-by-layer polymers, determination of optimal nanowire field emitter density to maximize the field enhancement factor, design of bridged nanowires across metal electrodes to order to circumvent post-synthesis manipulation steps, electrical characterization of bridged nanowires, rationale solution-phase synthesis of long ZnO nanowires on optical fibers, fabrication of ZnO nanowire dye-sensitized solar cells on optical fibers, electrical and optical characterization of solar cell devices, comparison studies of 2-D versus 3-D nanowire dye-sensitized solar cell devices, and achievement of 6-fold solar cell power conversion efficiency enhancement using a 3-D approach. The thesis results have implications in nanomanufacturing scale-up and next generation photovoltaics.

The goal of this thesis was to develop a new drug-delivering material to deliver anti-inflammatory protein for treating OA. Our central hypothesis for this work is that a controlled release/presentation system will more effectively deliver anti-inflammatory protein therapies to the OA joint. The primary goal of this work was to synthesize a block copolymer that could self-assemble into injectable, sub-micron-scale particles and would allow an anti-inflammatory protein, IL-1ra, to be tethered to its surface for efficient protein delivery. The block copolymer incorporated an oligo-ethylene monomer for tissue compatibility and non-fouling behavior, a 4-nitrophenol group for efficient protein tethering, and cyclohexyl methacrylate, a hydrophobic monomer, for particle stability. We engineered the copolymer and tested it in both in vitro culture experiments and an in vivo model to evaluate protein retention in the knee joint. The rationale for this project was that the rational design and synthesis of a new drug- and protein-delivering material can create a modular polymer particle that can deliver multi-faceted therapies to treat OA. This work characterizes the in vitro and in vivo behavior of our polymer particle system. The protein tethering strategy allows IL-1ra protein to be tethered to the surface of these particles. Once tethered, IL-1ra maintains its bioactivity and actively targets synoviocytes, cells crucial to the OA pathology. This binding happens in an IL-1-dependent manner. Furthermore, IL-1ra-tethered particles are able to inhibit IL-1beta-induced NF-kappaB activation. These studies show that this particle system has the potential to deliver IL-1ra to arthritic joints and that it has potential for localizing/targeting drugs to inflammatory cells of interest as a new way to target OA drug treatments.

The graphene moiré superstructure formed on Ru(0001) (g/Ru(0001)) has shown the potential as a template to self-assemble super-lattices of metal nanoparticles as model catalysts. To explore the possibility of rational catalyst design on g/Ru(0001), detailed density functional theory (DFT) calculations have been performed to investigate the adsorption and diffusion of Rh and Au adatoms on g/Ru(0001). The consequences of different hopping rates for cluster nucleation have been explored by performing Monte Carlo-based statistical analysis, which suggests that diffusing species other than adatoms need to be taken into account to develop an accurate description of cluster nucleation and growth on this surface. DFT calculations have also been carried out to investigate the adsorption and diffusion of 18 4d (Y-Ag) and 5d (La-Au) transition metal adatoms on g/Ru(0001). Given the necessity to study larger diffusing species than adatoms, DFT calculations have been performed to study the adsorption and diffusion of Rh and Au dimers and trimers on g/Ru(0001). It was shown that the mobility of Rh clusters decreases with the increase of cluster size, while for Au, dimers diffuse faster than monomers and trimers on the moiré surface. We then used a genetic algorithm combined with DFT calculations to predict the lowest energy structure of a Au8 cluster on g/Ru(0001). Our prediction leads us to propose that Au clusters aggregates through Oswald ripening with Au dimer being the major diffusing species. Finally, we examined the morphology of a Cu19 cluster on g/Cu(111) using MD simulations with COMB3 potential. We also studied the mobility of Cu clusters on g/Cu(111) at elevated temperatures. The analysis suggests that g/Cu(111) may not be a suitable substrate for the formation and growth of isolated Cu clusters. All these calculation results have provided us a better understanding and useful insights into the nucleation and growth mechanism of metal clusters on graphene moiré.

For polymer-matrix composites (PMCs) that contain insulating matrices and conducting fillers, the electrical properties of the PMCs are especially sensitive to the local concentration of the fillers in the matrix. For PMCs that have phase-segregated microstructures, better prediction of the properties is possible since enhanced control over the distribution of the filler in the matrix can be achieved. In this research, PMMA-ITO nanocomposites were chosen as the composite system in which to explore alternative microstructures, specifically highly phase-segregated microstructures. The microstructures were primarily controlled by varying the ITO particle size and concentration, and the fabrication parameters used to form the nanocomposites. The motivation for this research was to develop correlations between the microstructure and non-destructive measurements in order to improve the predictability of properties in percolating PMCs. As a result of this work, a novel phase-segregated microstructure was discovered, where ITO aggregate-wire structures self-assembled during the composite forming process. Structural analysis of the specimens was conducted primarily using transmission optical microscopy and scanning electron microscopy (SEM). Impedance spectroscopy and optical spectroscopy were the primary NDE characterization tools used for analyzing the variations among the specimens. Ultra-small angle x-ray scattering (USAXS) and stereological techniques were also used to describe the dimensions of the ITO aggregate-wire structures that self-assembled in the PMMA-ITO nanocomposites.

Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Sandhage, Kenneth H.; Committee Co-Chair: Snyder, Robert L.; Committee Member: Sanders, Thomas H.

Chromonic liquid crystals are a relatively new class of lyotropic liquid crystals. In an effort to understand this lyotropic phase better, studies on the phase behavior, defects formed in these systems and characterization of the order were performed. We studied three chromonic liquid crystal materials in nematic and biphasic regions: Sunset Yellow FCF (SSY, a food dye), a cationic perylene diimide derivative (PDI, a conducting dye) and cromolyn sodium (DSCG, a drug). For SSY chromonics in the nematic region, order parameters ( and ) were obtained by polarized Raman measurements. Using the order parameters the flow behavior was predicted and was found to be non-flow aligning. A comprehensive viscoelastic property set of SSY chromonics was obtained by studying the statics and dynamics of defects during the formation of planar aligned monodomain. Applications of PDI thin films as vapor sensors were explored; anisotropic electronic properties of oriented PDI films show good conductivity along the columns presumably arising from the overlap between the ? systems. In the biphasic region, growth and fluctuation of SSY tactoids and interesting patterns of biphasic DSCG under capillary geometry were observed; elastic properties and surface tension were estimated based on the shape of DSCG tactoids. Polymer dispersed lyotropic chromonic liquid crystals with different drop shapes and director configurations were also fabricated using various water-soluble polymers.

The generation of nanostructured assemblies with complex (three-dimensional, 3D) self-assembled morphologies and with complex (multicomponent) tailorable inorganic compositions is of considerable technological and scientific interest. This research demonstrates self-assembled 3D organic templates of biogenic origin can be converted into replicas comprised of numerous other functional nanocrystalline inorganic materials. Nature provides a spectacular variety of biologically-assembled 3D organic structures with intricate, hierarchical (macro-to-micro-to-nanoscale) morphologies. Morphology-preserving chemical conversion of such readily available, structurally complex templates will provide a framework for chemical conversion of synthetic organic templates and, potentially, production of organic/inorganic composites. Four research thrusts are detailed in this dissertation. First, chemical conversion of a nanostructured bioorganic template into a multicomponent oxide compound (tetragonal BaTiO₃ via layer-by-layer surface sol-gel coating and subsequent morphology-preserving microwave hydrothermal processing was demonstrated. Second, photoluminescence was imparted to bioorganic template structures through morphology-preserving chemical conversion to exhibit both the dramatic change in properties such processing can provide, and the potential utility of chemically transformed templates in anti-counterfeiting / authentication applications. Third, the reaction mechanism(s) for morphology-preserving microwave hydrothermal conversion of TiO₂ to BaTiO₃, were studied with the aid of Au inert markers on single crystal rutile TiO₂. Finally, constructive coating techniques (SSG) and moderate temperature (< 500C) heat treatments were utilized to modify and replicate structural color and were coupled with deconstructive focused ion beam microsurgery to prepare samples for microscale structure/property interrogation. Specifically, the effects of coating thickness and coating composition on reflection spectra of structurally colored templates were examined. Also, the effects of the replacement of natural material with higher index of refraction inorganic materials on optical properties were studied. The three processing research thrusts constituting chapters 1, 2 and 4 take advantage of moderate temperature processing to ensure nanocrystalline materials, either for shape preservation or to prevent scattering in optical applications. The research thrust presented in chapter 3 examines hydrothermal conversion of TiO₂ to BaTiO₃, not only to identify the reaction mechanism(s) involved in hydrothermal conversion under morphology-preserving conditions, but also to introduce inert marker experiments to the field of microwave hydrothermal processing.

This thesis begins with a brief analysis of the synthetic methodologies utilized in polymer science. A conclusion is drawn inferring that upper limits in molecular design are inevitable, arising as a direct consequence of the predominance of covalent strategies in the field. To address these concerns, the universal polymer backbone (UPB) concept has been hypothesized. A UPB has been defined as any copolymer, side-chain functionalized with multiple recognition elements that are individually capable of forming strong, directional, and reversible non-covalent bonds. Non-covalent functionalization of these scaffolds can lead to the formation of a multitude of new polymer structures, each stemming from a single parent or universal polymer backbone. To prepare such a UPB, isomerically pure exo-norbornene esters containing either a PdII SCS pincer complex or a diaminopyridine residue were synthesized, polymerized, and copolymerized via ROMP. All polymerizations were living under mild reaction conditions. Kinetic studies showed that the kp values are highly dependent upon the isomeric purity but completely independent of the terminal recognition units. Non-covalent functionalization of these copolymers was accomplished via 1) directed self-assembly, 2) multi-step self- assembly, and 3) one-step orthogonal self-assembly. This system shows complete specificity of each recognition motif for its complementary unit with no observable changes in the association constant upon functionalization. To explore potential applications of this UPB concept, random terpolymers possessing high concentrations of pendant alkyl chains and small amounts of recognition units were synthesized. Non-covalent crosslinking using a directed functionalization strategy resulted in dramatic increases in solution viscosities for metal crosslinked polymers with only minor changes in viscosity for hydrogen bonding motifs. The crosslinked materials were further functionalized via self-assembly by employing the second recognition motif, which gave rise to functionalized materials with tailored crosslinks. This non-covalent crosslinking/functionalization strategy could allow for rapid and tunable materials synthesis by overcoming many difficulties inherent to the preparation of covalently crosslinked polymers. Finally, the current status of the UPB concept is reviewed and methodological extensions of the concept are suggested. Evaluation of how UPBs may be used to optimize materials and their potential use in fabricating unique electro-optical materials, sensors, and drug delivery vesicles are explored.