Two closely related series of hydrocarbon polymers that contain mesogenic units interconnected by flexible methylene spacers along the main chain were prepared. The liquid crystalline properties of these two series of polymers were studied by differential scanning calorimetry (DSC), polarized light optical microscopy (POM) and X-ray diffraction. The first series of hydrocarbon polymers having biphenyl mesogenic units and polymethylene spacers in the main chain were prepared by a nickel catalyzed carbon-carbon coupling reaction. Polymers with number average molecular weights in the range of 4000 to 6000 have been obtained. Homopolymers with spacer units varying from 6 to 10 methylene units and equimolar copolymers with 6/8, 6/10, and 8/10 methylene spacers were found to exhibit smectic mesophases. The effect of the variation of the lengths of the methylene spacers on liquid crystalline properties is discussed. In general, increasing the length of the methylene spacers is accompanied by a decrease in the isotropization temperature. An alternating odd-even effect in transition temperatures is also observed with the even members having higher isotropization temperatures than the odd members. Two different X-ray diffraction patterns for odd and for even membered homopolymers were observed for unoriented samples. The second series of hydrocarbon polymers having tolan mesogenic units and polymethylene spacers in the main chain were prepared by a palladium catalyzed carbon-carbon coupling reaction. Polymers with number average molecular weights in the range of 3000 to 4000 have been obtained. Four polymers with 6, 8, 10 and 12 methylene spacers were prepared and they were found to exhibit smectic mesophases. Lengthening the polymethylene spacer between the tolan mesogenic groups decreased both the melting points (T$\sb1$) and the isotropization temperatures (T$\sb{\rm i}$) and also narrowed the mesomorphic ranges.

The thermodynamics of narrow molecular weight distribution binary blends of polystyrene/poly(alpha-methylstyrene) (PS-P$\alpha$MS) have been studied. The range of miscibility of these blends as a function of molecular weight has been determined by differential scanning calorimetry and optical techniques. Neutron scattering in the miscible region using the random phase approximation was used to determine the interaction parameter and correlation length. The temperature and composition dependence of these parameters were also obtained. Flory-Huggins-Staverman theory and Koningsveld's empirical "g" parameter were used to fit the temperature and composition dependence of the interaction parameter determined from neutron scattering data. The interaction parameter shows a composition dependence, in contrast to some previous studies. The temperature dependence of the neutron scattering has been measured for the first time for this system, and suggests LCST behavior should be observed for this system in the molecular weight range studied. Previous researchers' work shows this system to have a UCST, but our phase behavior data are in agreement with equation of state LCST predictions of Cowie and McEwen. An explanation as to why the LCST behavior has not been observed by light scattering techniques is presented.

Polyurethanes containing the biphenyl mesogen were synthesized and characterized by differential scanning calorimetry, wide-angle X-ray scattering and polarizing optical microscopy. One polyurethane (D6T24), which has an asymmetric structure, displays a monotropic smectic mesophase. The crystallization and mesophase-forming behavior of D6T24 is highly dependent on molecular weight. Another polyurethane (D6T26), which has a symmetrical structure, also displays a monotropic smectic mesophase. Because the crystalline unit cells of D6T24 and D6T26 are significantly different, combining the two polyurethanes in copolymers and blends suppresses crystallization, and in some cases produces enantiotropic systems. Blends of D6T24 and D6T26 containing more than 30% D6T24 by weight, and a random copolymer containing 47% D6T24 repeat units and 53% D6T26 repeat units, form enantiotropic smectic mesophases which do not crystallize. Annealing at high temperatures appears to transform the blends into copolymers, probably by means of transurethanification reactions.

This research was motivated by theoretical and experimental objectives regarding blends of thermotropic liquid crystalline polymers and flexible coil polymers with specific application to in situ fiber-reinforced composites. The primary aim has been the prediction of the phase behavior of blends and diblock copolymers containing rigid (liquid crystalline) species. The objective was to first derive a free energy expression that went beyond the mean field theories by taking composition fluctuations into account. Computational procedures were then developed for the evaluation of the free energy. The analytical derivation and the computational procedures provide the means for predicting the phase behavior of blends and diblocks as a function of molecular weight. The connectivity of the diblock molecule is shown to be responsible for a shifting of the isotropic-nematic transition in composition and a lowering of the critical $\chi$ value. A critical examination of the theory is difficult due to the lack of experimental data required for comparison. A secondary aim was to resolve some specific questions about a novel blend system that shows good prospects as an in situ composite. Investigation concerned the effect of blend composition on crystallization, the nucleating properties of the liquid crystalline component relative to those of more common nucleating agents, and the degree of miscibility between the blend components. The liquid crystalline component was shown to decrease crystallinity with increasing concentration. Its nucleation properties were similar to those of more common nucleating agents. No evidence of immiscibility was found in the blend system.

In the first half of this dissertation, density functional theory of first order transitions was used to describe the ordering phenomena of amorphous diblock copolymers. The resulting formalism was then applied to the ordering of symmetric diblock copolymers to the lamellar morphology for values of $\chi$N above the microphase separation transition. $\chi$ refers to the Flory interaction parameter and N is the number of statistical segments comprising the copolymer. Three distinct regimes for the N dependence of the domain space, D, were identified. For 10.495 $<$ $\chi$N $<$ 12.5, the weak segregation limit is realized where D is proportional to N$\sp{0.5}$. For $\chi$N $>$ 105, the strong segregation limit is achieved where D is proportional to N$\sp{0.67}$. Between these limits, for 15 $<$ $\chi$N $<$ 95, a new regime with characteristics distinctly different from those of the weak and strong segregation regimes was found. Within this "intermediate" regime, D is proportional to N$\sp{0.72}$ and the domain boundaries support substantial fluctuations. The distinct features of the microscopic density profiles in the various regimes are discussed. In addition, density functional theory was employed to investigated the phase behavior of non-symmetric diblock copolymers. In the second half of this dissertation, Monte Carlo simulations were performed in order to study the dynamics of a polyelectrolyte chain in three-dimensional random porous media with an applied electric field. It was found that the dependence of the chain mobility, $\mu$, on the number of segments comprising the polymer, N, is in qualitative agreement with actual gel electrophoresis experiments. Further, three regions for the N dependence of the mobility were identified and determined to be a function of the average size of the polyelectrolyte in relation to the average pore size in the random medium. In the region of small N, the mobility is influenced primarily by collisions with the random media. As the average size of the polymer becomes comparable to the average pore size, the existence of entropic barriers has the effect of introducing a strong dependence of the mobility on N. In the high N regime, the polymer chains become significantly entangled with the random medium, further impeding the motion of the chains. However, in this high N regime, the chain dynamics cannot be explained by reptation. Lastly, it was demonstrated that the chain dynamics of a polyelectrolyte in the presence of a regular array of obstacles with an applied electric field defers from the dynamics of a chain in a random medium. Indeed, it was demonstrated that the presence of random medium gave rise to a much more efficient separation of polyelectrolytes of different N.

Entanglement is one of the most important--but poorly understood--effects that occur in polymeric materials of high molecular weight. This work studies aspects of three long-standing problems--self-entanglement in a ring polymer, mutual entanglement between a ring and a rod, and network self-entanglement--and their solutions, by means of computer simulation. In self-entanglement, ring polymers are represented with the off-lattice rod-bead model. Perfect unbiased model instances are produced that have between N = 32 and 2048 beads, produced at several different values of bead radius, to represent polymers in solvents of varying quality. The topological state of each ring is represented with the Alexander polynomial. It is observed that the probability of observing a trivial knot $(P\sb{U})$ has a decreasing exponential dependence on the contour length (N) of the polymer, or that $P\sb{U}(N)=\exp(-N/N\sb0).$ The characteristic length $(N\sb0)$ varies by many orders of magnitude depending on solvent quality. In mutual-entanglement, a ring polymer is represented with the off-lattice rod-bead model, as in the study of self-entanglement. An infinitely long spike of zero radius is inserted at a (minimum) distance r from the center of mass of the ring, and the resulting system is deemed to be entangled if the resulting Gauss winding number (GWN) between the ring and the spike is zero. For a Gaussian chain with no excluded volume, the probability of a non-zero GWN is given by ${\cal P}(r,N)\approx A\exp(-(r/R\sb{g})\sp2/2B),$ where A = 0.7, B = 0.8, and $R\sb{g}$ is the radius of gyration of the ring. Cases where the ring has excluded volume and the spike has non-zero radius are also studied. Finally, a reasonable mathematical definition is provided of what might constitute "entanglement" in terms of a polymeric network. Model instances of networks are created given various initial compositions, and physical and virtual cross-links are both counted. The ratio of virtual to physical cross-links, $R\sb{e},$ depends strongly on the parameters which are used in the formation of the network. We suspect that entanglement effects are significant in rubber elasticity, but they are by no means of paramount importance.

The effect of specifically interacting functional groups (sticky foot) located at the chain ends of polystyrene on the adsorption rate, adsorbance, graft density and surface excess are discussed from cyclohexane, a theta solvent and toluene. Polystyrenes with hydroxyl and carboxylic acid end-groups (PS-OH, PS-COOH, HO-PS-OH and HOOC-PS-COOH) in narrow molecular weight distribution are synthesized by anionic polymerization of styrene followed by suitable termination reactions. Thin layer chromatography (TLC) is developed as an analytical technique to predict trends in the adsorption of the polymers in a range of solvents. In particular the information about the location of the end-group and therefore different chain architectures at the interface are inferred from this simple technique. Adsorption isotherms are obtained for each of the functionalized polymers of four different molecular weights, the selection of which was based on the TLC results. Kinetics of adsorption and the adsorbance data are determined by liquid scintillation counting of tritium labelled polymers. Graft density and surface excess data are calculated from the adsorbance data and other known parameters. It is shown, from these data, that polystyrenes with a carboxylic acid end-group form weakly stretched brushes at the glass-cyclohexane interface and mushrooms at the glass-toluene interface a result consistent with the higher osmotic repulsions towards packing in good solvents. Polystyrenes with functional groups at both the chain ends are hypothesized to form a range of structures from those dominated by tails at higher concentrations to those dominated by loops (in a good solvent) and trains (in a theta solvent) at lower solution concentrations. At higher molecular weights it is shown that functionalized polystyrenes behave as though they are not functionalized a result consistent with the TLC predictions. Hydroxyl end-group is shown to be an ineffective sticky foot from its adsorbance vis-a-vis polystyrene. The segment density distribution away from a polished silicon surface for a carboxylic acid end-functionalized polystyrene adsorbed from cyclohexane is determined by neutron reflection technique. The dry film thicknesses of polymer modified glass surfaces are determined by x-ray photoelectron spectroscopy. It is shown from the water contact angle data that a highly hrdrophilic surface of glass is converted to a completely hydrophobic surface by the adsorption of the functionalized polystyrenes. (Abstract shortened by UMI.)

In the first part of this thesis, we consider the physical phenomena accompanying the growth of highly branched polymers through computer simulation. The resultant dendritic molecules have unique properties arising from their "modified" Cayley tree branching pattern. We first consider growth of starburst molecules with flexible spacers separating tri-functional branch points. A self-avoiding walk algorithm is employed to kinetically grow the molecules. From the intramolecular density profiles of these structures, we find that the branch ends traverse the molecule throughout growth and are not confined to its surface. Further we observe that the branches are highly folded at all stages of growth. We observe power law relationships correlating the radius of gyration of the molecule to its molecular weight, M, and spacer length, P, finding in general: $R\sb{g}\sim M\sp\rho P\sp\nu$ with $\rho=0.22\pm 0.05$ and $\nu=0.50\pm 0.05$ at high molecular weights. From this we predict the hydrodynamic characteristics of the molecule. We then explore generalizations of the starburst structure by considering first the effect of branch stiffening, and second, the effect of changes in dendrimer connectivity by considering a related structure, the comb-burst. We repeat our study described above for these structures. In general we observe similar behavior to that described above, however slightly modified due to the structural modifications employed. The second part of this thesis addresses polymeric systems exhibiting the phenomenon of self-assembly. The specific problem under consideration is the characterization of phase transitions in diblock copolymer systems using density functional theory. We present a comprehensive, general scheme which allows the characterization of microphase separation of A-B diblock copolymer systems in terms of observed physical phenomena at all degrees of segregation. Our method is based on the density functional theory of Melenkevitz and Muthukumar and uses the technique of density profile parameterization to greatly reduce the technical complexity of the solution. We find that the microphase separated systems pass through three stages of ordering as the system is quenched. These are the weak, intermediate, and strong segregation regimes. We have calculated the phase diagram for three ordered morphologies: lamellae, hexagonally-packed cylinders, and body-centered-cubic spheres. We also characterize these microphases by the dependence of the lattice constant, D, and the interfacial width, $\sigma\sb{o},$ on the quench parameter $\chi N.$ We correctly reproduce the behavior predicted by previous theories describing the weak and strong segregation regimes. Through investigation of $D\sim N\sp\alpha,$ we find that $\alpha$ depends on both block length and morphology in the intermediate segregation regime. We attribute this behavior to chain stretching arising from the phenomenon of localization.

An investigation of acid-base interactions and zinc transition-metal complexations in ionomeric blends of sulfonated poly(ethylene terephthalate) (PET) with pyridine containing polymers will be discussed in relation to the level of specific intermolecular interactions, as measured with FTIR, and the degree of compatibilization, as observed from DSC and DMTA. Two pyridine containing polymer systems were evaluated: (1) a novel main-chain thermotropic liquid crystalline polyester containing pyridine dicarboxylate units, and (2) poly(ethyl acrylate-co-4-vinyl pyridine). Model thermotropic liquid crystalline polyester systems were developed and screened based on a set of macromolecular structure requirements directed toward future blends studies with PET and PBT. The first investigation discussed the preparation and characterization of TLCPs based on the biphenyl mesogen, 4,4$\sp\prime$-bis(6-hydroxyhexoxy)- biphenyl, BHHBP. Two series of TLCPs were prepared and characterized by CPOM, DSC, and WAXD. Both series of polymers exhibited smetic A phase types. The second investigation discussed the preparation and characterization of thermotropic liquid crystalline polyester based on the triad mesogen monomer, 4,4$\sp\prime$- (terephthaloyldioxy)dibenzoyl dichloride, (ClHTHCl). Various dihydroxy flexible spacers having chemical substituents similar in structure to the repeat units of PET and/or PBT were copolymerized with ClHTHCl and evaluated by CPOM, DSC, and WAXD. From this investigation, a series of polymers were characterized as an enantiotropic nematics. From this series, a candidate was selected as a model system, where the composition of flexible spacers was: 75% bis(4-hydroxybutyl) terephthalate and 25% 1,6-hexanediol. The flexible spacers of the model system was then modified to contain pyridine dicarboxylate units. This modified model system (TLCP$\sb{\rm N}$) was characterized as having a similar phase and phase-temperature relationship when compared to the model system. Upon development and characterization of TLCP$\sb{\rm N}$, ion exchange procedures were developed to exchange the sodium ions of PET-SO$\sb3$Na for hydrogen and subsequently hydrogen ions for zinc. Stoichiometric blends of both the free acid and zinc neutralized form of sulfonated PET were prepared and characterized by FTIR, DSC, and DMTA. For both these blends there was no evidence for specific intermolecular interactions or compatibilization. In the final investigation, both the free acid and zinc neutralized forms of sulfonated PET were blended with poly(ethyl acrylate-co-4-vinyl pyridine). The stoichiometric blends were prepared and characterized similar to the previous study. A zinc blend containing 77% sulfonated PET (7% SO$\sb3$Zn) and 23% poly(ethyl acrylate-co-4-vinyl pyridine) (10.6% VP) appeared to be predominately single phase by DSC and partially phase separated by DMTA. Where similar blends containing 58% poly(ethyl acrylate-co-4-vinyl pyridine) (5.2% VP) appear partially phase separated by both DSC and DMTA.

Several carbonyl-selective reactions were carried out with semicrystalline poly(ether ether ketone) (PEEK) film to assess the reactivity of the diaryl ketones at the film-solution interface. Surface analyses with X-ray photoelectron spectroscopy (XPS), attenuated total reflectance infrared spectroscopy (ATR IR) and contact angle measurement indicate that a thin layer of reagent-induced functionality results from these derivatizations in roughly 50% reaction yield. Data obtained indicate that derivatized surfaces can be functionalized further. Several PEEK-alcohol surfaces were prepared containing primary, secondary and tertiary alcohols, and the secondary and tertiary species were chain extended by reaction with lithium diisopropylamide and ethylene oxide. Primary alcohol groups were introduced by reacting PEEK with acetaldehyde lithiopropyl ethyl acetal and subsequent deprotection. Secondary alcohols were produced by reducing PEEK with Red-Al$\circler$ reagent, and tertiary hydroxyls result from reaction with methyllithium. In general, the alcohol surfaces were reactive toward electrophiles. XPS and contact angle measurement were used to follow surface reconstruction in heat-treated samples containing specific concentrations of surface active polystyrenes (SAP) in a polystyrene matrix (Mn = 10 K). The objective was to determine how certain molecular and environmental parameters influence surface reconstruction. The SAPs were prepared with three different architectures: the first (SAP:E-1) (Mn = 1, 5, 10, 40 and 100 K) contained a single perfluoroalkyl endgroup, the second (SAP:E-2) (Mn = 10 K) contained two fluorinated endgroups and the third contained a single perfluoroalkyl group in the middle of the chain (SAP:M-1) (Mn = 10 K). SAP:E-1 samples were annealed at different temperatures (180, 150, 110$\sp\circ$C and room temperature) for varied lengths of time (24, 48, 72, 96, 120 h and two weeks) to determine optimum annealing conditions to maximize surface fluorine enrichment (as detected by XPS). Comparison of these data indicate the effect of increasing polystyrene tail length on surface-activity of perfluoroalkyl groups. Optimum annealing conditions were used for heat treatment of SAP:E-2 and SAP:M-1 samples and comparisons were made on the basis of differences in architecture.