The syntheses of a series of new thermotropic liquid crystalline homopolymers, copolymers, and polymer blends, as well as their monomers were discussed. These polymers were prepared from 1,10-decane bisterephthaloyl chloride and substituted hydroquinones, and had a general structure as follows: where X = (CH(,2))(,(eta)) -H; n = 0, 1, 2, 3, ......, 10. or X = Br, -CN, -NO(,2), -OCH(,3). In the copolymers, X was either -CN or -OCH(,3) of different ratios. The structures and the thermotropic properties of these polymers were characterized by inherent viscosity measurements, gel permeation chromotagraphy, ('13)C-NMR, differential scanning calorimetry, and polarizing microscopy observations. All of the polymers had fairly low melting temperatures, which were desirable for thermotropic liquid crystalline polymers, and most of them had a mesophase (very likely nematic) above the melting point. As an example, the ethyl-substituted polymer had a melting point of 71(DEGREES)C and an isotropization temperature of 127(DEGREES)C. The substituent effects on the thermotropic behavior of these polymers were systematically studied in terms of both steric and polar effects. Increasing the size of the substituents resulted in the decrease of the thermal stability of the mesophase, while the higher polarity of the substituents resulted in a higher stability. With some success a theoretical treatment was developed which partly answered the questions which arose from the different behavior of polymers with different substituents; for example, why the methoxy-substituted polymer was (to the author's suprise) non-liquid-crystalline. The copolymerization of monomers with different substituents was found to be a good way to lower the melting point of the polymers. Copolymerization also caused a steady change in the mesophase thermal stability with changing composition of the copolymers. Observations on the optical microscopy revealed that no phase separation occurred in the mesophases of the blends formed from two different thermotropic polymers. However, the liquid crystalline polymers were immiscible with a non-liquid-crystalline polymer, and consequently both phase separations and phase inversions were observed with changing combination of the two components of these blends.

The objective of this dissertation was the synthesis of a water soluble vinyl polymer which could model some of the properties of hemoglobin such as oxygen and carbon dioxide carrying capacity, hydrophobic domains and rigidity. The selection and synthesis of functional monomers was very important in the development of a model of hemoglobin. Derivatives of hemin, dimethylester (HDME), di-3-(1-imidazolyl)propylamide (HDA) and mono-3-(1-imidazolyl)-propylamide monomethylester (HMEMA), were synthesized to function as oxygen carriers. The bulk of the polymer was poly(styrene) whose function was to provide hydrophobic domains. Three monomers, methyl p-vinylbenzenesulfonate (MSS), 4-vinylpyridine (4VP) and p-vinylbenzylchloride (VBC), were incorporated in the polymer at 13 - 20 mol % and gave water solubility subsequent to hydrolysis of the ester, quaternization of the amine or substitution of the chlorine with a trialkylamine respectively. p-Azidophenyl methacrylate (APMA), a photoactive crosslinking agent, was polymerized to give structural rigidity. Amine moieties, 2-aminoethyl methacrylate (AEMA) and N-methacrylylhexamethylenediamine (NAHD) were incorporated to carry carbon dioxide as a function of pH. The reactivity of these monomers was characterized and the reactivity ratios were utilized to prepare ter- and tetrapolymers of known composition. Heme monomers behaved as chain terminators except in the presence of strong ligands for iron. Polymeric subsets of the five different types of monomers were characterized as simple models of hemoglobin. The kinetics of the oxygenation of HMEMA showed that oxidation is due to dimerization. Polymer bound HMEMA was 1.5 times more stable to dimerization but also exhibited some autooxidation. ('13)C-NMR experiments, used to study the formation of carbamate as a function of pH in amine-containing polymers, proved that the pK(,a) of the amines was too high to bind ('13)CO(,2) at physiological pH. Dye solubilization experiments demonstrated the presence of hydrophobic domains in the model polymers which were favored at high hydrophobe content and ionic strength and low solution concentration. These polymer molecules aggregated in solution at concentrations greater than 0.1 - 0.2 weight %. Preliminary evidence suggested that photolysis of APMA caused intramolecular crosslinking of the polymer. Novel hydrophobic polyampholyte gels were observed in polymers containing hydrophobic, anionic and cationic groups.

Abstract not available

Abstract not available

Abstract not available

Abstract not available

A study of the influence of the drying process in developing fiber properties during the dry-jet wet spinning of poly (p-phenylene benzobisthiazole) is undertaken. The fiber's structure and mechanical characteristics from the coagulated state through the drying process to the as-spun and heat treated state are investigated herein. The wet fiber is composed of a swollen macro and microfibrillar network of highly oriented molecules with lateral but no longitudinal order and exhibits a high degree of mechanical anisotropy. The structural and mechanical features of the as-spun fiber appear to develop during coagulation. The drying process during drying is characterized by a distinct radial contraction and axial elongation due to the porous and anisotropic nature of the coagulated fiber. Alterations in the structure and mechanics of PBT fibers are observed upon drying which is rationalized in terms of the collapse process. The drying process is a fiber modification phase. High temperature and tension are employed to optimize the driving force toward property enhancement during the drying stage. Tension during drying straightens the wet fibrillar network while offsetting axial compressive internal stresses whereas the use of high temperature increases the extent of the lateral molecular order and increases molecular orientation resulting in enhanced tensile properties. The compressive strength and shear modulus increase after drying suggesting that removal of water may serve to enhance lateral interactions within the swollen fibrillar network inhibiting shear and compressive deformation and the onset of buckling instabilities. Further increases in the compressive strength through high tension and temperature drying are not achieved since further enhancements in intermicrofibrillar and fibrillar associations are speculated to be minimal. A force-temperature (F-T) technique is implemented to study thermal expansion characteristics of these rigid rod aromatic fibers through examination of the reversible F-T behavior. Subsequent mass loss and microstructural changes during the F-T experiment (an effective post processing heat treatment) is detected from irreversible F-T effects. An assessment of the effectiveness of the initial drying and heat treatment processing to induce thermal stability and material alterations is obtained through this F-T technique.

No description available.

No description available.

Note: