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An A-B monomer containing an ether group, 4(4-acetoxyphenoxy) benzoic acid (PAPBA) was successfully synthesized via a new route using 4-methoxyphenol and 4-chlorobenzonitrile as starting materials. Another ether containing monomer, 4(2-acetoxy-6-naphthoxy) benzoic acid (PANBA), which appears to be a novel monomer, was also prepared in high yields from 6-methoxy-2-bromonaphthalene and ethyl-4-hydroxybenzoate via the Ullmann condensation reaction. These monomers were found to be useful for synthesizing LCP copolymers and segmented copolymers. A variety of polyarylates based on 5-tertiary butylisophthalic acid were synthesized via melt acidolysis techniques. The resulting high molecular weight polyarylates were amorphous polymers and the t-butyl groups along the polymer backbones were found to be thermoxidatively stable. Thermotropic liquid crystalline polyesters (LCPs) are well known for their thermoxidative stability, ductility, solvent resistance and the potential of generating extremely strong, stiff molecular chains. In this dissertation research, several novel liquid crystalline aromatic polyether-ester copolymers were synthesized by the incorporation of an A-B monomer, either PAPBA or PANBA, into the polymer main chain. The corresponding copolymers were thermoxidatively stable and melt processable over a wide compositional range. Novel carboxyl terminated oligomers of an amorphous engineering polymer, poly(arylene ether ketone)(PEK) were successfully synthesized. The synthetic method was somewhat similar to that of carboxyl terminated poly(arylene ether sulfone) oligomers. The PEKCOOH oligomers were quantitatively endcapped and their molecular weights could be controlled. Thermogravimetric analysis revealed that the PEKCOOH oligomers were thermoxidatively stable and therefore suitable for high temperature post-reactions. In general, thermotropic liquid crystalline polymers show excellent properties in the longitudinal direction. Nevertheless, to improve the transverse mechanical properties of liquid crystalline polymers, novel poly(arylene ether ketone)-LCP segmented copolymers were synthesized via melt acidolysis techniques. Chemically bonding an isotropic engineering thermoplastic into a potentially liquid crystalline anisotropic polyester affords segmented copolymers which may possess a balance of mechanical properties in both the longitudinal and transverse directions. In the case of PEK-poly(oxybenzoate)(PEK-POB), a limited amount of POB (~25 wt %) could be incorporated so as to produce segmented copolymers which would yield coherent films. On the other hand, when PEK-POB was modified by adding PAPBA to form PEK-POB-POPB segmented copolymers, a series of the segmented copolymers with various compositions was realized. The liquid crystalline behavior was found to be retained in the segmented copolymers, depending on the degree of the LCP content. The structural analysis of the A-B monomers mentioned earlier was performed by elemental analysis, mass spectroscopy, proton NMR and FT-IR. All the polymers synthesized were characterized by thermal analysis (DSC and TGA). The molecular weight of the carboxyl terminated PEK oligomers was determined by an automatic titration method, and indirectly, by intrinsic viscosity measurements. The latter method was also used to assess the molecular weight of the amorphous polyarylates. For liquid crystalline polyether-ester copolymers and PEK-LCP segmented copolymers, DSC and hot stage optical microscopy were utilized to investigate their thermotropic liquid crystalline behavior. DMTA was used to determine the high temperature properties of the polymers and tensile tests, i.e. stress-strain data, were employed to obtain information on their mechanical properties. / Ph. D.

The range of polymeric materials containing the Si-O bond spans from the three-dimensional inorganic networks of silica (SiO₂), to linear high molecular weight polysiloxanes which display properties of both organic and inorganic materials. Part 1 of this dissertation describes the synthesis of three-dimensional inorganic SiO₂ networks and organic-inorganic hybrid networks using a low temperature solution technique known as the sol-gel process. During this process, hydrolysis and subsequent condensation of inorganic alkoxides (most often tetraethylorthosilicate, TEOS) in the presence of catalysts leads to the formation of three-dimensional SiO₂ networks. However, the strong acid or base catalysts typically employed in sol-gel reactions would also cause undesirable degradation of many organic modifiers, especially at higher temperatures required for the drying of the gels. A catalyst-free sol-gel process, based on tetramethyl orthosilicate (TMOS), the most reactive silicon tetra alkoxide in the series, was developed. The catalyst-free route provides an optimum reaction environment for the synthesis of organic-inorganic materials through copolymerization reactions. This concept will be exemplified by two organic-inorganic systems in which TMOS was used as the inorganic component while poly(dimethylsiloxane) and polyimide oligomers respectively, were employed as the organic component. The effect of such modifications on the surface and bulk properties of the inorganic SiO₂ networks was also investigated. Part 2 of this dissertation describes specific aspects associated with the synthesis of amine containing polysiloxane oligomers. A new molecular design which allows for independent control of molecular weight and amine functionalities was developed. The new synthesis involves anionic ring opening equilibrium copolymerization of the cyclic siloxane tetramer D₄ with a new cyclic siloxane monomer containing amine functionalities as pendant groups on silicon atoms. The effect of the bulky substituent {-CH₂CH(CH₃)CH₂NHCH₂CH₂NH₂} of the silicon atom on the position of thermodynamic equilibrium, and the extent of molecular weight and composition control in the linear polysiloxane oligomers was studied. / Ph. D.