Graft copolymers of conjugated poly(3-hexylthiophene) and polypeptides containing an artificial amino acid, 3-thienylalanine (3TA), were synthesized and purified using solid phase synthesis techniques. The structures of the graft copolymers were characterized by NMR, and binding of biotinylated graft copolymers to avidin and streptavidin was studied using fluorescence spectroscopy. The hydroxmethylbenzoic acid (HMBA) solid phase resin linker was stable in the presence of an oxidative polymerization catalyst, ferric chloride, for up to five hours as shown by infrared spectroscopy and elemental analysis. A two-level factorial design was used to identify three factors which had statistically significant effects on the solution fluorescence emission maxima of the copolymers: catalyst to monomer ratio, monomer addition rate, and addition of bithiophene. Additionally, two two-factor interactions had significant effects: the interactions of monomer ratio and monomer concentration, and of monomer ratio and addition of Proton-Sponge. A peptide containing 3TA and biocytin, separated by a triglycine spacer, was synthesized on HMBA resin and characterized by mass spectroscopy fragmentation and by two-dimensional correlational NMR spectroscopy. The peptide, and an analog substituting biocytin with an acetylated lysine, were produced in 84 to 89% purity The integrity of the peptide backbone and the successful copolymerization were confirmed by 2D NMR after polymerization. Number average molecular weights of 7300 g/mol for the acetylated lysine copolymer, and 10 850 g/mol for the biocytin copolymer could be estimated from the NMR spectra. Strong fluorescence emission maxima at long wavelengths were observed for the copolymers, indicating high conjugation lengths. This system is not limited to peptides and 3-hexylthiophene, and should be generally applicable to synthesis of copolymers of conjugated polymers and biomolecules that can be immbolilized on a solid support.

The free-radical polymerization of a series of α-substituted acrylic acid derivatives has been achieved by using hydrostatic pressure as a kinetic and thermodynamic driving force. It is shown that conducting polymerization in a range of pressures between 1 and 9 kbar dramatically improves the polymerizabilities of the investigated acrylates, opening the way to the synthesis of high-molecular weight polymers in short reaction times. The polymerizabilities of α-alkylacrylates at ambient pressure, obtained by extrapolation from high-pressure kinetic data, correlate well with Meyer's steric parameters for the relevant α-alkyl group. While the polymerization of α-alkylacrylates with linear alkyl groups proceeded via a vinyl double-bond addition in a traditional way, methyl α-isobutylacrylate polymerized though alternating steps of addition and 1,5-hydrogen transfer from the penultimate unit to provide an isomeric α-branched polymer structure. Structure-property relationships for the synthesized poly(α-substituted acrylates) have been investigated. Increasing the size of the α-alkyl group decreases thermodynamic stability of the poly(α-alkylacrylates), and facilitates their thermal and photo-degradation. Conformational transitions of poly(α-alkylacrylic acid)s in aqueous solutions are shown to be highly dependent on the size of the α-alkyl group. The transition pH can be fine-tuned by adjusting the total hydrophobic content of the polymer via copolymerization of α-alkylacrylic acid with different alkyl substituents. A high-pressure reversible addition-fragmentation chain transfer (HP-RAFT) protocol for controlled/living free-radical polymerization has been developed. It is demonstrated that this HP-RAFT technique can be used to livingly polymerize sterically hindered monomers, such as methyl ethacrylate, to provide polymers with low polydispersities, controlled molecular weights and end-groups. A methodology for the synthesis of well-defined poly(ethacrylic acid) has been developed. The controlled polymerization of polystyrene-methacrylate macromonomers has been achieved by HP-RAFT, providing densely branched comb-like polymers with controlled molecular weight characteristics. The synthesis of linear-comb diblock copolymers is also achievable by this technique. The HP-RAFT polymerization of traditional monomers, such as methyl methacrylate (MMA), has been investigated. It is demonstrated that the methodology allows for the synthesis of ultra-high molecular weight polymers with low polydispersities. The technique was used to obtain well-defined PMMAs with molecular weights of more than one million.

Hydrogels are of interest to the biomedical field because the hydrated networks can provide a physiological environment where biological species can survive or grow. Genetic engineering of protein polymers—a synthetic technique which provides a superior level of synthetic control without compromising natural composition—was used to prepare materials of the general architecture, rod-coil-rod. A naturally occurring motif, the leucine zipper, describes the rod domain. The leucine zipper can self-assemble when two amphipathic helices come together and are stabilized by contact along their hydrophobic face. The acidic leucine zipper domain, denoted ‘A,’ contains mostly glutamic acid in residues which flank the hydrophobic interface. A polyelectrolyte protein, of the repetitive sequence [(AG)3PEG], defines the coil domain, denoted ‘C.’ AC10Acys displayed reversible gelation as a function of pH and temperature, thus three aspects of the viscoelastic behavior were investigated. The gelation properties were studied by single particle tracking, which monitors the Brownian motion of fluorescent particles imbedded in a protein hydrogel or suspended in a protein solution. First, the physical crosslinks in an AC10Acys hydrogel network were diplaced by the addition of a leucine zipper domain, Atrp. A 2.23 mM AC10Acys hydrogel behaved as an elastic gel at pH 8.5, but upon addition of 1.13 mM Atrp, a viscous solution was obtained. Second, the effect of charge of the leucine zipper domains were examined using, AC10Acys, and BC10Bcys, where ‘B’ denotes a basic leucine zipper domain. Both protiens form viscous solutions at 1.78 mM, pH 8.5 or pH 7.4, however, upon combination of AC10Acys and BC10Bcys, a stiff elastic gel is formed. Finally, a series of triblock proteins with increasing midblock length were genetically engineered to study the influence of midblock length on the gelation behavior of triblock proteins. The pH and concentration dependences of gelation of ACxAcys, where x = (20, 30, 40, 50), were examined by single particle tracking. Whereas AC10Acys was found to gel around 2.23 MM, pH 8.0, the concentration required for gelation decreases to 1.27 mM for the protein with the longest midblock length, AC50Acys.

The effects of molecular architecture on morphological behavior of block copolymers for four types of architectures have been investigated. In Chapter 2, the morphological behaviors of a group of polystyrene-polybutadiene (PS-PBD)C cyclic block copolymers and their corresponding linear polystyrene-polybutadiene-polystyrene (PS-PBD-PS) triblock copolymer precursors were investigated across a range of morphologies. The contour length and the volume fraction of the cyclic block copolymers obtained are essentially identical to that of their corresponding linear triblock copolymers. Therefore, morphological difference due to compositional mismatch between the cyclic and triblock copolymer pair is eliminated. It is found that when the cyclic and its triblock copolymer form the same morphology, microdomain periods of cyclic block copolymers are all smaller than those of the corresponding linear triblock copolymer precursors. This is resulted from the portion of chain segments that adopts their trajectory parallel to the interface in cyclic block copolymers and thus does not contribute to domain spacing. When different morphologies are formed between the cyclic and triblock pairs, the interface tends to curve away from the linked end-block side in cyclics compared to their triblock copolymers. In Chapter 3, lamellar spacings of a series of (PS)n(PI) n star block copolymers, with n = 1, 2, 4, 16, were studied. Among the series, all the PS blocks are of same length and all the PI blocks have the same molecular weight. Lamellar spacings of the stars (n = 2, 4, 16) were compared directly with that of the diblock copolymer (n = 1). A significant increase in lamellar spacing with increasing junction point functionality (n) was found in this series of materials and can be attributed to molecular crowding near the junction point. Chapter 4 and chapter 5 discussed the effect of chain architecture on the morphological and tensile properties of series of multigraft copolymers. By applying the “constituting block copolymer concept”, the physical behavior of these molecules was compared with the existing theories. It is found that morphological behavior of grafted copolymers can be well predicted using this theoretical approach. The material property, however, is controlled by both the chain architecture and the morphologies thus formed.

By anchoring random copolymers to the substrates, the interfacial interactions were tuned precisely and dependence of the orientation of lamellar microdomains in thin films on interfacial interactions was investigated quantitatively. A critical film thickness was found, below which a parallel alignment of the lamellar microdomains was seen throughout the film and depends upon the strength of the interfacial interactions. The electric field alignment process is a competition between the applied electric field and surface fields. In the early stages, the surface field dominates. A mixture of orientations of the lamellae was found if the interfacial interactions were not balanced. However, in the presence of lithium ions (210ppm), lamellar microdomains were aligned along the applied electric field direction throughout the film, regardless of the strong interactions of blocks with substrate. For cylindrical microdomain forming diblock copolymer thin films, starting from a poorly-ordered state, surface fields and opposed electric fields biased the cylinder orientation. With time upon annealing, the cylinders are locally disrupted to form ellipsoidal shape microdomains that connected into cylinders in the applied field direction. Starting from an ordered state with cylinders parallel to the surface, the applied field enhanced fluctuations at the interfaces of the microdomains and disrupted cylinders into spheres. This transition is similar to thermoreversible cylinder-to-sphere order-order transition. With time, the spheres deformed into ellipsoids and reconnected forming cylindrical microdomains oriented at ∼45° with respect to the applied field, which subsequently aligned along the field direction. These studies were complemented by studies on an electric field induced disordered sphere-to-cylinder transition in thin films. Under an electric field, the asymmetric diblock copolymer formed spherical microdomains that were deformed into ellipsoids and, with time, interconnected into cylindrical microdomains oriented in the direction of the applied electric field. A route to control the microdomain orientation in three dimensions in diblock copolymer thin films was also studied by use of two orthogonal, external fields. An elongational flow field was applied to obtain an in-plane orientation of the microdomains of the copolymer melt and an electric field, applied normal to the surface, was then used to further align the microdomains.

A new approach to surface modification of materials has been formulated and explored in great detail. It was shown that polyvinyl alcohol (PVOH) quickly and irreversibly adsorbs to hydrophobic surfaces producing smooth, continuous, hydrophilic, robust films in the thickness range of tens of angstroms. Surfaces of all hydrophobic materials studied could be successfully turned hydrophilic by this adsorption, which is performed from dilute aqueous solutions of PVOH. The ultra-thin films of adsorbed PVOH were studied by means of contact angle, ellipsometry, XPS, AFM, FT-IR, and DSC. Adsorption conditions, such as time, polymer concentration and molecular weight, temperature, salt type and concentration, and polymer composition all have an effect on the properties of the adsorbed film. The unique character of PVOH irreversible adsorption among other water-soluble polymers is explained by polymer crystallization that occurs concurrently with adsorption. Crystallinity within adsorbed films is demonstrated by the means of FT-IR and DSC. Chemical properties of adsorbed PVOH were studied, and a number of synthetic procedures were developed for further modification of PVOH ultra-thin films. Cross-linking of adsorbed PVOH imparted great stability in hot water. PVOH in the ultra-thin films was successfully converted into a variety of polyvinyl esters and urethanes; polyethylene glycol was grafted “to” and “from” these films. Prospective applications of PVOH adsorption and its ultra-thin films were studied. Improved adhesion in glued joints of polyethylene was demonstrated when PVOH was pre-adsorbed on PE before applying adhesive. PVOH adsorption and subsequent PEG grafting significantly reduced protein adsorption on a hydrophobic surface. A possibility to create defined features on PVOH surface by chemical patterning was demonstrated. A novel design of vapor sensing devices based on the adsorbed and modified PVOH was proposed and studied in detail. It was shown that remarkable reproducibility in PVOH adsorption on surface acoustic wave devices can be achieved and that further chemistry of the adsorbed films permits the preparation of sensitive and selective vapor sensors.

Subjecting a liquid/liquid interface to an electrohydrodynamic pressure enhances fluctuations of a characteristic wavelength, leading to an instability and eventually the formation of well-defined columnar structures. Extending the linear stability analysis of a single fluid interface to a liquid/liquid bilayer produced generalized results applicable to any interface. Countering the electrohydrodynamic pressure is the Laplace pressure, which is dictated by the surface energy or the interfacial energy. Consequently, the characteristic length scale for the bilayer instability is reduced. Results presented for different polymer bilayers under a wide range of experimental conditions show quantitative agreement with the generalized theory with no adjustable parameters. Data over four orders of magnitude in reduced wavelength and field strength can be described by the theory. External electric fields are also used to amplify interfacial fluctuations in a air/polymer/polymer system where one polymer dewets the other. Two different hydrodynamic regimes are found as a function of electric field strength. For weak fields, heterogeneous nucleation can lead to the formation of holes before the electrostatically driven instability sets in and the dewetting kinetics are not influenced by the electric field. Stronger electric fields lead to a spinodal instability that causes the formation of polymer columns on top of the second polymer. In addition, the analysis of the polymer-polymer interface during the early stage of the instability indicates a slip boundary condition for the upper layer on the lower fluid substrate. Columnar structures with a characteristic hexagonal order increase in diameter at a rate dictated by a balance of the forces exerted on the surface of the columns and on the underlying reservoir. If the reservoir is exhausted, or if dewetting occurs, the columns are isolated and growth is arrested, kinetically trapping the size of the columns. An alternative way to control structure formation at the surface of a thin liquid film is presented by creating topographical patterns comprised of stripes with well defined widths. It is seen that undulations beneath a stripe pattern lead to the formation of columns. The width of the stripes is seen to markedly alter the wavelength of lateral growth of the fluctuations.

The effects of phase behavior and the molecular architecture on morphological behavior of graft copolymers for three types of architectures have been investigated. In Chapter 2, the effects of homopolymer on the formation of T-junction grain boundaries have been studied in a blend of polyisoprene homopolymer and a single graft block copolymer I2S with two equal length blocks of polyisoprene and one arm of polystyrene linked at a common junction point. While T-junctions were previously observed to be quite rare compared to other tilt grain boundary morphologies such as chevrons and omegas, they were found in abundance in the blend used in the current study. Simple free energy calculations show that the homopolymer present in the blend stabilizes the cylindrical curvature of the end caps, rendering the T-junction morphology more stable in blends than in neat block copolymers. This agrees with the observed greater frequency of occurrence of the T-junctions in our blend sample than in neat block copolymers. In Chapter 3, we report the observation of a lyotropic phase transition between the lamellar and cylindrical morphologies in a mixture of polystyrene-polyisoprene Y-shaped single graft copolymer with a lower molecular weight homopolyisoprene. The nature of the intermediate structures which form as the transition progresses has been examined via transmission electron microscopy (TEM) and Wigner-Seitz cell analysis with simple free energy arguments. The shapes of grains of cylindrical morphology have been analyzed via an adaptation of Wulff construction and simple interfacial free energy calculations. In Chapter 4, nucleation of cylindrical morphology at chevron, omega and T-junction grain boundaries is observed in blends of homopolyisoprene and I2S single graft block copolymer in which two arms of polyisoprene (PI) and one arm of polystyrene (PS) are linked at a common junction point. Chapter 5 and Chapter 6 discuss the morphological behavior of organic-inorganic randomly grafted copolymers and trifunctional multigraft copolymers, respectively. By applying the results from the recently established mean-field theory, we study the microphase segregation of organic-inorganic randomly grafted copolymers. For trifunctional multigraft copolymers, "constituting block copolymer concept" is used to understand their morphological behavior.

In order to gain a better understanding of structure-property relationships, particularly the influence of regular versus random branching on the crystallization and polymer morphology of polyethylene, and to obtain chemical control over chain folding and lamellar thickness, model polyesters were synthesized and thoroughly characterized by solid-state NMR. Polyesters with perfectly regular placement of defects along the backbone were obtained by melt polycondensation of long-chain aliphatic α,ω-diols and 13C-labeled short-chain branched and non-branched diacids, diluting the amount of ester functionalities along the backbone by steadily increasing the length of the employed diols from 22 to 32 and then 46 methylene units. Wide-angle X-ray diffraction established that the minimum diol length necessary to produce polyethylene-like orthorhombic crystal structures is 32 methylene units. A non-branched system used as a benchmark for comparison of long-chain polyesters to polyethylene showed polyesters to possess a polyethylene-like crystal structure with diester layers. This shows that these long-chain polyesters are valid model systems for polyethylene. However, chain dynamics in the polyester crystallites were found to greatly differ from those in polyethylene. This must be attributed to the diester layering prohibiting chain diffusion. Small-angle x-ray diffraction of regularly branched polyesters showed the desired control over lamellar thickness, which is invariable under varying crystallization conditions and thermal treatment. The regular placement of the non-crystallizable defects enforces quantization of the length of non-crystalline chain folds. The resulting marked length difference between tight and loose loops affects the crystallinity significantly. Crystallinities determined by solid-state direct polarization NMR were found to be well above 50%, proving tight chain folds. The location of ester moieties and their mobility was probed by 1H spin diffusion and wideline separation NMR, showing ester groups to be located either on the crystalline/amorphous interface or in the amorphous regions, depending on the length of the diacid segment. Finally, diacid segment conformations were probed by DOQSY NMR, which showed specific conformations of ester moieties compatible with tight chain folds. Future research on this topic should focus on the variation of side groups, incorporating functional groups or reactive side groups that allow for post-polymerization modification of the crystalline/amorphous interface.

The application of polymeric media as sensors, drug delivery agents, chromatographic columns, enzyme mimics, and many other functions is driven by the ability of the polymer to participate in molecular recognition events. The polymer provides a three-dimensional local environment that surrounds the binding site, which is one of the major factors that govern the binding efficiency. The local environment plays a crucial role in both the solid and solution state and will be explored here. The design, synthesis, and characterization of molecularly imprinted polymers (MIPs), highly crosslinked polymers obtained in the presence of host-guest complexes, will be discussed. Using biologically inspired three-point hydrogen-bonding as the recognition motif, a fundamental study to characterize binding pre- and post-polymerization binding, guest molecule transport, and binding site heterogeneity will be presented. The fundamental understanding of the imprinting process obtained will be shown to be necessary for the development of real-time, highly selective MIP-based sensors. Using π-stacking, effective sensing for polychlorinated aromatic contaminants in water will be demonstrated. A modified strategy, surface-templated polymer films, provides an ideal platform for the real-time, selective detection of bacteria at environmentally relevant concentrations. In the solution state, living polymerization methodologies are utilized to systematically explore the factors (molecular weight, backbone composition, chain flexibility) that affect a soluble polymer's ability to bind a guest molecule.