Single polymer passage through geometrically confined regions is ubiquitous in biology. Recent technological advances have made the direct study of its dynamics possible. We studied the capture of DNA molecules by the electroosmotic flow of a nanopore induced by its surface charge under an applied electric field. We showed theoretically that the DNA molecules underwent coil-stretch transitions at a critical radius around the nanopore and the transition assisted the polymer passage through the pore. To understand how a polymer worms through a narrow channel, we investigated the translocation dynamics of a Gaussian chain between two compartments connected with a cylindrical channel. The number of segments inside the channel changed throughout the translocation process according to the overall free energy of the chain. We found a change in the entropic driving force near the end of the process due to the partitioning of the chain end into the channel rather than the initial compartment. We also developed a theory to account for the electrophoretic mobility of DNA molecules passing through periodic confined regions. We showed that the decrease in the translocation time with the molecular weight was due to the propensity of hairpin entries into the confined regions. To further explore the dynamics of polymer translocation through nanopores, we performed experimental studies of sodium polystyrene sulfonate translocation through α-hemolysin protein nanopores. By changing the polymer-pore interaction using different pH conditions, we identified the physical origins of the three most common event types. We showed that increasing the polymer-pore attraction increased the probability of successful translocation. Motivated by understanding the dynamics of a polymer in a crowded environment, we investigated the dynamics of a chain inside a one dimensional array of periodic cavities. In our theory, the chain occupied different number of cavities according to its confinement free energy which consisted of entropic and excluded volume parts. By assuming that the chain moved cooperatively, the diffusion constant exhibited Rouse dynamics. Finally, we performed computer simulations of a chain inside a spherical cavity. We found that the confinement effect was best described by the hard sphere chain model. We further studied the escape dynamics of the chain out of the cavity through a small hole. The equilibrium condition of the chain during the escape was discussed.

The majority of this dissertation focuses on proton conducting materials that could be used at high operating temperatures. Higher operating temperatures are desirable as they will increase fuel cell efficiency, reduce cost, and simplify the heat management system. The factors governing proton conduction including segmental mobility, protogenic group identity, and charge carrier density were investigated on a variety of polymers containing 1H -1,2,3-triazole moieties. Proton conductivity measurements were made using AC impedance spectroscopy. Random copolymers and terpolymers of triazole-containing acrylates and poly(ethylene glycol)methyl ether acrylate (PEGMEA) have been synthesized. Conductivity increased with increasing degree of PEG incorporation until reaching a maximum at 30% mole PEGMEA. In comparison to benzimidazole-functionalized polyacrylate with 35% mole PEGMEA, the triazole analog showed a higher proton conductivity, and a less pronounced conductivity temperature dependence. Further increases in conductivity was achieved through the addition of trifluoroacetic acid. To study the effect of charge carrier density on proton conduction, polyacrylates containing a different number of triazole groups per repeat unit were synthesized. The result showed that introduction of more than one triazole per repeat unit did not result in an increase in conductivity as there was an accompanying increase in Tg. To improve the thermal and mechanical properties, triazole groups were tethered to a higher T g backbone polymer, polynorbornene. Introduction of polyhedral oligomeric silsesquioxane (POSS) into triazole-functionalized polynorbornene was also investigated. In a parallel set of investigations, poly(2-(dimethylamino)ethyl methacrylate), PDMAEMA, and copolymers of DMAEMA and methyl methacrylate (PDMAEMA-co-PMMA) were synthesized via atom transfer radical polymerization (ATRP). Fluorescently-labeled PDMAEMAs were synthesized using fluorescent ATRP initiators to ensure the presence of one dye molecule on every polymer chain. PDMAEMAs and PDMAEMA-co-PMMA with different molecular weights have been deposited onto a negatively-charged silica surface via controlled flow deposition. The results show that the polymer deposition rate depends on molecular weight, and is inversely proportional to molecular weight. A preliminary adhesion study of 1-ìm negatively charged silica spheres onto these functionalized surfaces indicates that by varying the molecular weight, the adhesion threshold can be changed. System modeling is being conducted to support experimental observations.

Ionic liquids (ILs), neoteric salts with Tm < 100°C, have garnered vast interest due to a number of unique properties including vanishingly low volatility, non-toxicity and property tunability. Many polymers were found to dissolve in ILs, and polymer solution properties were measured using the room temperature IL 1-ethyl-3-methylimidiazolium ethylsulfate, [EMIM][EtSO 4], as a model IL. Polyethylene glycol (PEG) dissolves in [EMIM][EtSO 4] above ∼60°C, the neat polymer's melting temperature, and if concentration and molecular weight are high enough, the solution transforms into a semi-transparent gel at lower temperature. Thermoreversible gelation is traced to kinetically frustrated polymer crystallization, a mechanism established previously for many pairings of crystallizable polymer with aqueous or organic solvent. Negatively and positively charged polymers dissolve in [EMIM][EtSO 4], typically over long time periods, and solution chain properties are measured using common physiochemical techniques. Electrostatic interactions of sodium poly(styrene sulfonate) are screened without the need of added salt due to the presence of the charged solvent and size-molecular weight relationships indicate sodium poly(styrene sulfonate) assumes a coiled conformation in solution. Lysozyme dissolves in [EMIM][EtSO4] assuming an expanded conformation with compromised secondary structure, the unfolded structure stabilized by the IL. Preferential solvation of dissolved lysozyme in mixed [EMIM][EtSO 4]/H2O solvents prevents lysozyme aggregation above its denaturation temperature.

Because of their important role in many areas of science and technology, polymer brushes have been extensively studied theoretically and experimentally. In the first part of my thesis, in order to understand the molecular weight behavior of polymer brushes, a new method to cleave polymer brushes were investigated. A new inimer (having both an initiator and monomer fragment) was synthesized. After growing polymer brushes from these inimers containing cleavable linkages, the polymer brush layers were characterized by various techniques. The brush chains were cleaved and collected, providing an opportunity to study and compare polymer grown in solution vs. polymer grafted from the inimer-inbedded surfaces. Molecular weight differences were determined since it has been assumed, but not confirmed, that polymers synthesized in both manners should have the same molecular weight. Since growing a brush layer from a photopolymer (PP) layer is different than growing brushes from the surface directly, the first part of my thesis is dedicated to showing the differences between these two surfaces and how the PP network affects the brush growth with using different characterization methods such as neutron reflectivity and secondary ion mass spectroscopy. These studies helped to understand the characteristic behavior of the polymer brushes such as where the initiation occurs, how the inimer concentration affects on the photopolymer properties. The next part of my thesis is about the possible applications of polymer brushes. We examined the antibacterial effects of –onium salts and enzymes attached to polymer brushes. It is already known that -onium salts can be used as antibacterial agents in solution. They can kill both Gram-positive and Gram-negative bacteria. In our case, polymer brushes were grown from the PP layer spin-coated on glass substrates, and we investigated their antibacterial effectiveness of these polymer brushes. Phosphonium salts and lysozyme were used as antibacterial agents. Lysozyme was chosen since it is biocompatible and can be used inside the body. Lastly, azobenzene-containing photoresposive polymer brushes were prepared and the surface properties before and after UV exposure were observed. The surface wettability changes dramatically, and using only UV light is one of the safest and cleanest way to alter surface properties.

This thesis describes research in the control over long-range order and orientation of porous nanoscale materials and liquid mobility on surfaces with patterned chemistry and topography. A variety of researches will cover the topics ranging from preparation of ordered block copolymers and anodized aluminum oxides, and dynamic wettability on chemically patterned wafers with or without topography. The structure evolution of BCP thin films exposed with binary solvent mixture vapors at different temperatures will be investigated by scanning force microscopy and grazing incidence small angle X-ray scattering. The swollen thin films will undergo typical phase separation depending on thickness, temperature, and exposure time, which will determine the morphology of the resulting porous templates. A new approach for preparing ordered nanoporous AAO will be demonstrated using the pattern transfer of BCP structures to the surface of aluminum. By solvent annealing the BCP films in solvent vapor, arrays of cylindrical microdomains with a high degree of lateral order will be produced. Using reactive ion etching, the template of the nanoporous film will be transferred to the Al surface and the subsequent anodization in a concentrated acid solution will generate channels with the center-to-center distance and lateral order of the BCP film. A study of drop mobility on a surface with patterned wettability will be the final topic in the thesis. Silane chemistry, selective etching, and microcontact printing will be used to prepare designs on chemically patterned wafers with topography. The samples will have two different areas; one on which a liquid drop will move easily and another that will restrict its motion. Dynamic contact angle measurements will then be performed on the surfaces to determine the effect on drop mobility. The objective is to show that both contact angle and contact angle hysteresis are important in regards to drop mobility. The growth of condensed water droplets on these surfaces will be viewed and recorded.

Naturally occurring horse spleen ferritin (HSF) bionanoparticles (BNPs) (12 nm in diameter) with magnetic cores (8 nm in diameter) are distinct from synthetic nanoparticles due to their perfectly defined size and shape, and abundant amino acid surface functionality. The theme of this thesis is the use of HSF BNPs as nanoscale building blocks for surface functionalization and directed assembly. Bioconjugation grafting chemistry was utilized to tailor the surface properties of HSF BNPs, and interfacial assembly techniques were applied to control the ordering of BNPs and integrate the functionalized BNPs into composite materials. By taking advantage of surface available amines on the exterior surface of ferritin BNPs, norbornene functionalities were attached by amidation of an N-hydrosuccimide (NHS)-functionalized norbornene. Norbornene functionalized ferritin BNPs were co-assembled with norbornene-functionalized CdSe/ZnS quantum dots at an oil/water interface to form robust, ultra-thin films and capsules upon crosslinking by means of ring-opening metathesis polymerization (ROMP). Ordered hexagonal arrays of gold nanodots on a silica substrate were prepared by block copolymer micelle lithography. PEGylated alkane thiols attached to ferritin BNPs enabled a specific interaction of BNPs with the gold nanodots through a thiol-gold linkage. As a result of the guided assembly of ferritin BNPs on the gold nanodots, highly ordered ferritin BNP arrays were achieved over a large area, and confirmed by grazing incidence small angle X-ray scattering (GISAXS). Grafting chemistry was performed to grow poly(methacryloyloxyethyl phosphorylcholine) (polyMPC), and poly(PEG methacrylate) (polyPEGMA), chains from the surface of ferritin BNPs using atom transfer radical polymerization (ATRP). The resulting hydrophilic polymer coatings were found to have a distinct impact on the recognition properties of the ferritin BNPs, as seen in their suppressed interactions with thin film polymer templates, and their resistance to antibody recognition. The solubility of polyPEGMA-coated ferritin nanoparticles in organic solvents enables their dissolution in the block copolymer polystyrene-b-poly (ethylene oxide) (PS-b-PEO), and selective integration into the PEO domains of microphase-separated copolymer nanostructures by self-assembly. This approach provides yet another interfacial assembly strategy to control the spatial distribution of polymer-grafted ferritin BNPs.

Nanoimprint lithography (NIL) has established itself as a competitive, high resolution and cost efficient alternative to standard photolithographic technologies. In the pursuit of the use of NIL in microelectronic and energy applications, such as fabrication of interlayer dielectrics and hybrid solar cells, we present our study on porous dielectrics and semiconductor nanowires generated by NIL. First, we developed a facile but powerful manufacturing route to fabricate air gap dielectrics with well-defined pore geometries. A thermally labile organic polymer, denoted as sacrificial template, was patterned using thermal NIL and embedded in a lowk dielectric thin film. Air gap nanochannels in the dielectric layer were obtained by selective removal of the patterned, sacrificial polymer through thermal degradation. Various process conditions such as film deposition, imprint, etch, and calcination were studied to deduce their effect on the air gap dielectric film formation. By finely tuning these parameters, crack free air gap dielectric films were produced. Introduction of air gaps effectively lowered the dielectric constant of the dielectric material since air has a dielectric constant of unity. These air gap structures demonstrated excellent electrical, thermal and mechanical properties making them attractive candidates as interlayer dielectrics for next-generation integrated circuit (IC) applications. In addition, we explored the suitability of the nanochannel dielectrics as fluidic devices and demonstrated successful fluid transport through these channels by fluorescence dye infusion experiments. Inspired by the above methodology, we further developed a new, potentially low-cost and high-throughput technique to fabricate highly crystalline, continuous cadmium selenide (CdSe) semiconductor nanowires by successfully merging electrodeposition and soft nanoimprint lithography. By utilizing nanoimprint patterned photoresists as templates during the electrodeposition step and subsequent resist lift-off, we were able to generate continuous parallel arrays of CdSe nanowires, each wire having dimensions dictated by the imprint mold. We demonstrated that the electrodeposited nanowires were highly crystalline and their crystalline structure was unaffected by the lift off process. Our method allowed production of well-aligned CdSe semiconductor nanowire arrays of precisely controlled diameter and length and led to a substantial improvement over the control in nanowire orientation compared to existing technologies. This economic and relatively simple approach can easily be implemented and adapted to various semiconductor systems and is expected to be used in photovoltaic applications.

Controlling the morphology of thin films is key in optimizing the efficiency of polymer-based photovoltaic (PV) devices. The morphology and interfacial behavior of the multicomponent active layers confined between electrodes are strongly influenced by the preparation conditions. Results obtained in this work quantitatively show the photovoltaic device performance is strongly affected by the nanoscopic morphology, crystal orientation, composition distribution and the interdiffusion behavior of the photoactive layer. To better understand the physics of the photoactive layer in the organic photovoltaic devices, it is necessary to gain a quantitative understanding of the morphology and the manner in which it develops. A key element in the kinetics associated with the structure development is the interdiffusion of the components. To that end we used poly(3-hexylthiophene) (P3HT) / [6,6]-phenyl C61-butyric acid methyl ester (PCBM) bilayers as a model to investigate the interdiffusion of the components and its role in the development of the morphology. A detailed description of the diffusion behavior and the morphology developed from a layer of P3HT in contact with a layer of PCBM during thermal annealing is given. Amorphous P3HT and PCBM are shown to be highly miscible and PCBM can penetrate into the P3HT layer through the P3HT amorphous region and form the bulk heterojunction structure within a few second of annealing at 150°C. The results indicated that one phase is a pure P3HT crystal domain and the other phase is the mixture of amorphous P3HT and PCBM, which is not consistent with a phase separation of the components by a spinodal decomposition mechanism. We put forth an alternative mechanism, namely a competitive crystallization/diffusion argument, to describe the origin of the morphology. These findings provide new insights and guidance in the generation of active layers in organic photovoltaics that are crucial in enhancing the device performance. Textured organic solar cells were also studied, providing another route to fabricate higher performance devices.

This dissertation describes research performed using siloxane polymers. This includes the reactions of siloxane polymers with inorganic oxide surfaces to form covalently attached monolayers, and the electrical properties of crosslinked silicone composite films fabricated by compounding with nickel particles. In addition to these topics, the use of contact line pinning as a practical and controllable method for the deposition of materials on superhydrophobic and chemically patterned surfaces is also described. The first chapter provides a general review of siloxane polymer chemistry, focusing in particular on the relationship between molecular structure and physical properties. The use and fabrication of silicone composite materials is also discussed, including typical methods for crosslinking siloxane polymers and the effects of filler materials. Finally, contact angle hysteresis and contact line pinning phenomena are presented. Following this introduction, four separate but interrelated projects are presented. First, the surface modification of titania via hydridomethylsiloxanes is discussed. This work represents an extension of the reaction of hydridosilanes and provides an environmentally clean method for the hydrophobization of titania. Linear and cyclic hydridomethylsiloxanes, as well as hydridomethylsiloxane-co-dimethylsiloxane polymers, are used as reagents and the resulting surfaces are discussed. Unpredicted results from this method lead to the consideration of poly(dimethylsiloxane) as a previously unconsidered reagent presented in the next project. The second project discusses the covalent attachment of siloxane polymers, particularly poly(dimethylsiloxane), to a range of inorganic oxide surfaces, including titania, nickel oxide, alumina, and silica. This reaction is presented as a thermally activated equilibrium process, and offers insight into certain aging processes found in silicone materials. Particular focus is made on the development of a highly reproducible method for the fabrication of low contact angle hysteresis surfaces. Furthermore, this reaction is shown to be general for the siloxane bond through the reaction of functional and cyclic siloxanes. The third project describes the preparation of electrically conductive silicone coatings, containing nickel and titania particles. The effect of nickel concentration and geometry on the electrical properties of these coatings is examined and the effects on the percolation threshold are presented. In addition to this, the addition of titania nanoparticles to diminish electrical conductance is also investigated. The fourth project discusses the contact line pinning of liquids on hydrophobic surfaces. In this chapter, the use of ionic liquids exhibiting no vapor pressure is used to experimentally determine the de-wetting process of liquids from pillared, superhydrophobic surfaces through micro-capillary bridge rupture. Furthermore, this technique is used as a preparative technique for the fabrication of individual salt crystals supported on pillared surfaces.

This dissertation describes research carried out in the area of siloxane polymers, which refers to a group of polymers based on alternating silicon-oxygen backbones. The inexpensive starting materials and extraordinary thermal, mechanical and optical properties make siloxane polymers promising materials in a lot of applications, such as lithography, optical devices, self-healing materials and ion conducting membranes. Four projects are described after the introduction section. In the first project, extremely crosslinked silicone networks with novel structure are prepared by hydrosilylation of two tetra-functional cyclic monomers, 1,3,5,7-tetramethylcyclotetrasiloxane (D4H) and 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasilxane (D4V). By introducing cyclic structures into the network and increasing the crosslink density, the thermal stability is improved, the Young's modulus and hardness of these siloxane networks are also be enhanced. In addition, some traditional properties of PDMS have been reserved, such as UV transparency, low surface tension and being reaction injection moldable. The second project involves using the extremely crosslinked silicone network from the first project as a replica material for both nanoimprint lithography (NIL) and capillary force lithography (CFL). Because the advantageous properties of D4H-D4V networks meet all the requirements of NIL and CFL, such as UV transparency for photo nanoimprint lithography, thermal stability for high printing temperatures, high modulus for high printing pressures, low surface energy for easy demolding and molecular smoothness for achieving small scale features, this material was tested to fabricate sub-25 nm scale patterns from blu-ray discs and sub-9 nm scale patterns from anodized aluminum templates. The third chapter describes a study on thermal reconstruction of oxygen plasma-treated poly(dimethylsiloxane) networks with controlled crosslink density. Instead of using a commercial product, e.g. Dow Corning Sylgard 184, pure silicone networks were prepared by hydrosilylation of various monomers and/or precursors. The relationship of reconstruction rate versus crosslink density is described. The fourth project involves in surface modification of extremely crosslinked silicones using a chemical method. A stable hydrophilic surface was prepared by peroxide oxidation. After incorporating silanol groups on the surface, subsequent modifications with various reactive silanes were conducted and control of surface properties was demonstrated. The hydrophilic surfaces show similar reactivity to that of oxidized silicon wafers. The last chapter describes a "living" siloxane network which has been used as a self-healing material. Through ring opening polymerization of octamethylcyclotetrasiloxane (D4) and bis(heptamethylcyclotetrasiloxanyl)-ethane (bis-D 4) in the presence of a quaternary ammonium catalyst, "living" siloxane networks with controlled crosslink density were prepared. Based on the equilibrium of cyclic and linear species, the "living" networks exhibit "self-healing" abilities and can be "reshaped" via chemical stress relaxation upon application of external mechanical stress. (Abstract shortened by UMI.)