The interactions between surfaces and polymer chains are at the heart of many polymer problems, such as flow in confined geometries, development of new nano-lithography methods, understanding of the structure of block copolymer grains, polyelectrolyte adsorption, and modeling polymer brushes. The latter two systems will be the focus of this dissertation. The physical properties of each system are studied using statistical mechanics, and results from computer simulations are presented. The first topic of this thesis is the study of adsorption of a polyelectrolyte chain in an electrolyte solution to a uniformly charged surface. By using off-lattice Monte Carlo simulations, the conditions of adsorption of a uniformly charged polyelectrolyte onto oppositely charged planar and spherical surfaces have been investigated. These conditions are functions of the strength of the electrostatic interaction, Debye screening length, chain length, charge density and curvature of the surface. The adsorption can be tuned by using anyone of these parameters. The chain's conformation, adsorption energy and thickness of the adsorbed polymer are obtained under different adsorption conditions. We find the Monte Carlo simulation data to be in good agreement with the theoretical prediction derived previously by using the assumptions of ground state dominance and separability. The second topic is on the adsorption transition of a uniformly charged polyelectrolyte onto heterogeneously charged planar surfaces investigated with Monte Carlo simulations. Each of these surfaces contains both positive and negative charges. In addition to the usual case of adsorption of a polyelectrolyte to a surface with net charge opposite to that of the polymer, we show that a polyelectrolyte can adsorb onto a surface with net surface charge density similar to that of the polyelectrolyte. This adsorption is due to the spatial inhomogeneity of the surface charges which creates attractive regions with charge density different from the overall charge density of the surface. The spatial inhomogeneity of the surface charges also leads to differences in the conformation of the adsorbed polyelectrolyte. The critical conditions of strength and range of electrostatic interactions and chain length necessary for adsorption of a polyelectrolyte to a heterogeneously charged surface are determined. The last topic deals with applying self-consistent field theory (SCFT) to polyelectrolyte brushes grafted onto uncharged curved surfaces with no added salt. The goal of this study is to test the validity of the Debye-Hückel approximation for the electrostatic interaction in polyelectrolyte brushes. Our results show that the Debye-Hückel approximation is a good approximation for a weakly charged polymer brush grafted on a surface with small radius. The geometry of the system also plays an important role in the validity of the Debye-Hückel approximation. The approximation gives better results in spherical geometry then cylindrical.

Two different series of condensation polymers were synthesized. Synthetic chemistry was used to obtain polymers with well-defined architectures; specifically, linear polymers were made with regularly-spaced “defects” along the polymer backbone. The resultant structures—both the fluorinated polyesters and the carboxylate ionomers—were characterized initially in terms of their crystal structures. It was found that fluorinated segments, when incorporated as “defects”, did in fact perturb the polymer crystal packing; however, exclusion of fluorine from the crystalline regions did not occur for the systems studied. The polyesters did exhibit interesting surface properties, but these properties could not be explained solely on the basis of polymer chemistry. The carboxylate ionomers, synthesized showed evidence of controlled crystal architecture. Their characteristic X-ray diffraction peaks were found to be directly dependent on both the number of carbons between neighboring carboxylate species and the identity of the counterion, suggesting the possibility of continuous lamellar clustering of the ionic species.

The phase separated structure of polyurethane foams is kinetically trapped due to the vitrification of hard segment domains, which results in an interconnecting hard domain morphology. This new morphological picture depicts the importance of the inter-connectivity provided by both the small portions of the long hard segments and the disordered regions that serve as an indirect bridge between hard domains. Deuterium substitution has been used to specify different regions of the interconnecting phase-separated structure in polyurethanes. Thin film samples were prepared isothermally using foam formulations with different water contents to obtain very different degrees of domain inter-connectivity. By analyzing the relative rate of substitution at different relative humidity and temperature of the environment, it is possible to differentiate the degree of phase separation for various samples with different degrees of phase separation. The infrared spectroscopic features, mainly amide vibrations, of various parts of hard segments have been identified. The deuterium substitution rates measured revealed that the size and dispersion of hard-segment domains can vary significantly as a function of reaction temperature and composition of reactants. It is also possible to differentiate the interfacial region from the phase-separated domains. Based upon the interconnecting hard domain morphology, infrared dichroic studies further demonstrated the contribution of hard domains to reinforcement of polyurethane materials. Plastic deformation within the hard domain was observed even at small strain, giving a molecular insight to the stress-softening effect and energy hysteresis associated with polyurethanes. The viscoelastic properties of polyurethane studied by stress relaxation experiments have again shown the importance of inter-connectivity to the overall mechanical properties of this material. A correlation between the exact water placement and overall deterioration of physical properties has been established. Lignin has been successfully incorporated as a reinforcing component to enhance polyurethanes. It was not until the dispersion state of the lignin in polyol was improved and both the processing conditions and catalyst package were optimized that the modulus and strength of the polyurethane material showed significant enhancement. It is found that lignin most likely functions as the hard segments to achieve better inter-connectivity of the physical network of the hard domain morphology.

Flows with strong extensional components are capable of unraveling and breaking dissolved polymer chains, yielding a distribution of chain fragments that continually alters the molecular weight distribution, MWD, of a given sample over time of exposure to the flow. The evolution of the MWD is described in terms of scission rates and probabilities along the polymer backbone that a scission event will occur. These scission event probability distributions, p(f), where f is the fractional position along the backbone, depend on the flow condition, and quantitative characterization of the breadth of p(f) by the standard deviation relative to chain length, R, reveals information about the configuration of the chain at the time of scission. In this thesis, we have developed a generalized scission kinetics formulation that does not make unsupported assumptions regarding p( f), and applied this formulation to the analysis of MWDs, measured by quantitative gel electrophoresis, and arising from degradation of NaPSS in both turbulent Taylor-Couette and sonication flows. For the first time, we have reported R for turbulent flow-induced degradation and found that essentially random scission best describes the degradation process, with R = 9.5 for a single Gaussian description. Including the possibility of scission of a folded chain as a dual Gaussian description we found similarly that Rsingle = 9.5 and Rfolded = 0.09, with 70% of the chains breaking via the folded pathway, but with negligible improvement in the error in fit. We contrasted this result with our result for scission in sonication flow. With the single Gaussian description, we found a best fit R = 0.28, and with the dual Gaussian description, we found best fit parameters of Rsingle = 0.17 and R folded = 0.09, with the folded chain breaking more than twice as frequently. The latter fit was reduced 30% in error from the single Gaussian fit. In developing our understanding of the technique of quantitative gel electrophoresis, we have developed fundamental models of the diffusion-mediated, post-electrophoresic staining process. The single and dual binding models accurately predict the edge-like appearance of the diffusing dye front which is not predicted by the Crank model37 of probe diffusion in a binding medium.

Aliphatic polyesters are widely used in biomaterial applications including drug delivery and tissue engineering because they are both biocompatible and biodegradable. However, these materials are primarily semi-crystalline, hydrophobic, solids at biologically relevant temperatures and lack functionality for altering their properties. Consequently methods to incorporate functional groups pendent to aliphatic polyesters and thereby tune their properties are sought. Pendent functionalization presents a significant challenge as the degradable nature of the polyester backbone severely limits the chemistry that can be performed without inducing degradation. The focus of this thesis is the preparation of pendent-functionalized aliphatic polyesters by controlled methods to give well-defined materials with a diverse range of functional moieties and physical properties. Pendent functionalization was achieved through the synthesis of α-substituted lactone monomers, followed by Sn(II) mediated ring-opening polymerization and post-polymerization modifications. Lactone monomers substituted with allyl, cyclopentene, and acetylene groups were prepared and their homo-/copolymerization chemistry was studied. Post-polymerization modifications that could be achieved without degradation or cross-linking were explored to give polyesters with dramatically altered properties relative to conventional aliphatic polyesters. Water-soluble PEG-grafted polyesters, as well as, polyesters with pendent oligopeptide sequences and drug moieties were prepared. The suitability of these materials for biomaterial applications was evaluated by cytotoxicity testing using mouse fibroblasts and human red blood cells. The application of the pendent-functionalized polyesters as polymer-drug conjugates and cross-linked microparticles was also explored.

Synthesis of well defined polymers containing metal complexes in the side chain is achieved either by the direct or the indirect approach. The direct approach utilizes NMP and RAFT to copolymerize 2,2':6',2''-terpyridine ligand (terpy) functionalized styrene (Styterpy) monomer in combination with other comonomers. The indirect approach produced polymers using ATRP technique containing either terpy or [Ru(terpy)2]2+ metal complex in the side chain. The indirect approach is considered the best method to obtain terpy or metal complex containing polymers in the side chain. Luminescence block-random copolymers containing [Ir(terpy)2] 3+ in the side chain were studied. Absorbance and emission spectra compared to a model compound shows that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the [Ir(terpy) 2]3+ containing copolymer studied in various solvents showed mono-modal aggregation with decreasing aggregate size as the solvent dielectric increased. The copolymer precursor P(S-b-ACterpy) shows multi-modal aggregation in different solvents with the majority population consistent with single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the metal complex. Homopolymers containing [Ru(terpy)2]+2 in the side chain are prepared in which the complex contained either a long hydrophobic C16-alkyl group or only hydrogen at the 4'-terpy position. The homopolymers containing the C16-alkyl groups showed lyotropic liquid crystalline (LC) behavior in chloroform solutions from room temperature to 60°C and self assembled in the bulk to form hexagonal arrays of cylinders. In addition, this alkyl side chain was observed to crystallize in the solid state. Homopolymers without the C16-alkyl group showed no lyotropic LC nor any crystallization behavior. Diblock and tetra-arm star copolymers containing [Ru(terpy)2] +2 with C16-alkyl group in the side chain were studied in which the diblock show lyotropic LC properties and microphase separate in the bulk into hierarchical cylinder-within-lamella morphology. The star polymer show birefringence and microphase separate in the bulk. Both copolymers have crystalline properties due to the C16-alkylgroup. The material design emphasizes the relationship between the molecular structure and self-organization of these polymers.

This dissertation investigates several aspects of an important research topic in polymer science, that is, morphological control in polymer nanostructures. A brief introduction is given in Chapter 1. In Chapter 2, the central issue is defect control in novel noncentrosymmetric (NCS) lamellar block copolymer blends, made from poly(styrene-b-butadiene-b-isoprene- b-cyclohexadiene) and poly(styrene-b-cyclohexadiene). Coexisting centrosymmetric (CS) and NCS lamellar morphologies were observed, as predicted by mean-field theory. Morphologies of NCS tilt and twist grain boundary defects are studied, and detailed analysis of interfacial energies associated with NCS twist grain boundaries are performed. Defects unique to NCS layered systems, such as versatile NCS kink bands and NCS polarity reversals, are also studied in detail. Based on these results, strategies for reducing certain NCS defects are proposed. In Chapter 3, the issue becomes morphological characterization of a new ABA triblock copolymer, poly(tert-butyl vinyl ether- b-isobutylene-b-tert-butyl vinyl ether) (P tBVE-PIB-PtBVE), a thermoplastic elastomer (TPE) and precursor for poly(vinyl alcohol-b-isobutylene- b-vinyl alcohol) (PVA-PIB-PVA). PtBVE-PIB-P tBVE samples with 23--39 wt% PtBVE content exhibited typical characteristics of TPE with tensile strengths of 9--15 MPa and elongations at break of 760--1300%, and formed lamellar or cylindrical morphologies, depending on molecular compositions. In Chapter 4, the subject shifts to crystal morphology characterization of a porous crystalline polymer (high density polyethylene, HDPE) prepared through a novel crosslinking-swelling-crystallization (CSX) process. Open pores with oriented lamellar structures in the pore walls were observed, much different from structures found in typical bulk HDPE. Based on the crystal morphology, possible mechanisms for the pore formation in the CSX process are proposed. In Chapter 5, results from two other polymer systems studied are summarized. For the first system, poly(styrene-b-ethylene butylene- b-styrene), the effects of solvent selectivity and annealing temperature on resulting morphologies are studied systematically. Spherical or lamellar morphologies were initially obtained from three selective solvents; upon thermal annealing all changed into cylindrical morphology. The second system is polydiacetylene (PDA) single crystals of bulk, micron, and submicron sizes. For both PDAs studied, the crystal lattice parameters do not change markedly with decreasing crystal size, suggesting other factors may contribute to the observed change in optical properties.

As a new frontier of foldamer research based on the synthesis and characterization of oligomers programmed to fold and self assemble into secondary structures continues to open, new scaffolds with a variety of dimensions are required. Presented here is the synthesis and characterization of a new ortho -Phenylene Ethynylene (o-PE) backbone scaffold. This scaffold has been synthesized using Sonogashira methods with a variety of building blocks containing π-rich and π-poor elements substituted with non polar and polar substituents. Solvent induced folding of these short oligomers into well defined helices was confirmed via 1D and 2D NMR methods. Utilizing the electron rich and electron poor phenylene building blocks, variations of these o-PE oligomers have been synthesized to determine the folded stability of π-rich vs. π-poor vs. π-poor/rich systems. Variations in temperature offer a route, aside from solvent denaturation, to probe the stability of the folded structures. This is the first report of a highly detailed solution NMR characterization using 1-D and 2-D methods examining the folding of a PE backbone without hydrogen bonds, and the first for an oPE system in general.

Polymers containing tethered benzimidazole revealed that the mitigating factors for proton conduction are segmental mobility and charge carrier density. In general increased mobility will result in increased proton conduction especially at temperatures below 160°C, however, reductions in charge carrier density (benzimidazole content) to achieve increased mobility adversely affect proton conduction above 160°C. Further improvements in proton conduction were achieved by copolymerization of a benzimidazole acrylate with 2-Acrylamido-2-methylpropanesulfonic acid, however, ionic crosslinking between sulfate and benzimidazolium negated any conductivity increases. Additional experiments with benzimidazole were not pursued due to inherently high Tg values of the resulting polymers. With the understanding that maximization of mobility and charge carrier density are necessary, the nature of the heterocycle was investigated. Polymers containing tethered 1,2,3-triazole were prepared and characterized. While some synthetic difficulties limited the impact, initial results indicated some improvements in proton conductivity in neat materials and large improvements in conductivity could be achieved by doping with up to 100 mol% trifluoroacetic acid (TFA). Additionally, inherently lower Tg materials result when using 1,2,3-triazole in place of benzimidazole. Improvements in monomer synthesis allowed further probing of 1,2,3-triazole as a protonic charge carrier, it was revealed that 1,2,3-triazole given equal charge carrier density and nearly identical Tg values, the use of 1,2,3-triazole as a substitute for benzimidazole results in materials with reduced conductivity. It was found through X-ray crystallographic studies and literature searching that a higher concentration of 1,2,3-triazole is required for productive proton transport due to tautomeric shifts in 1,2,3-triazole. The effect of charge carrier density and the effect of reduced heterocycle basicity for 1,2,3-triazole was determined by preparing polysiloxanes with tethered 1,2,3-triazole units. The polysiloxane backbone provided inherently low Tg materials to maximize mobility and allowed direct comparison with analogous imidazole containing polysiloxanes reported by Meyer. It was found that increasing weight fraction of triazole results in dramatic conductivity improvements, the pKa of the heterocycle does not play a significant role in proton conduction, and 1.5 to 2 orders of magnitude conductivity improvements are observed when the system is doped with up to 100 mol% TFA. Conductivity values of TFA doped siloxanes containing 1,2,3-triazoles are equal or slightly better than the analogous imidazole materials. The benefits to utilizing 1,2,3-triazoles are the versatility of synthesis using "click" chemistry and the ability to absorb equimolar amounts of an external acid, opening the possibility to further conductivity improvements using alternate low Tg backbones and complex systems utilizing both hydrated and anhydrous proton conduction domains.

Novel ester substituted poly(alkylene oxides) were prepared from ester substituted epoxide monomers, where the ester groups were separated from the epoxide groups by a series of 0 to 7 methylene spacer groups. The reactivity of these monomers using coordinate and cationic initiators was examined, with the objective of determining the proximity effect of the ester groups on the polymerizability of the monomers. Homopolymerizations of the ester substituted monomers using the Al(C(,2)H(,5))(,3)/H(,2)O/AcAc (1/0.5/1) coordinate initiator system demonstrated a strong proximity effect of the ester groups on the monomer reactivity. Those monomers with 0 to 3 spacer groups gave polymers in much lower yields with lower molecular weights than the monomers with 4 to 7 spacer groups. The polymers were semicrystalline, and became more rubbery as the number of spacer groups increased. Copolymerizations of the ester substituted monomers having 1, 2, and 5 spacer groups with several cyclic ethers, using the Al(C(,2)H(,5))(,3)/H(,2)O/AcAc (1/0.5/1) initiator system, also demonstrated a strong proximity effect. Copolymers of the ester substituted monomer with 1 spacer group were produced in very low yields, while copolymers of the ester substituted monomer with 2 spacer groups were produced in low to good yields. Copolymers of the ester substituted monomer with 5 spacer groups were produced in good to high yields. The level of incorporation of the ester substituted monomers into the copolymers was generally > 80%. Many of the copolymers were semicrystalline. Cationic homopolymerizations of the ester substituted monomers having 1, 2, and 5 spacer groups were carried out using BF(,3)(.)O(C(,2)H(,5))(,2) and Al(C(,2)H(,5))(,3)/H(,2)O (1/0.5) as initiators. The polymers from the BF(,3)(.)O(C(,2)H(,5))(,2) initiated polymerizations were low molecular weight, ranging from viscous liquids to paste-like solids. The monomers with 1 and 5 spacer groups gave high molecular weight polymers when the Al(C(,2)H(,5))(,3)/H(,2)O (1/0.5) initiator system was used, while the monomer with 2 spacer groups gave a low molecular weight material. Anionic homopolymerizations of the ester substituted monomers with 1, 2 and 5 spacer groups were attempted, but were unsuccessful. Propylene oxide could be polymerized, however.