Investigation of structure-property relationships of aromatic polyimides, polyamides, polydehydroalanines, and adamantyl-substituted methacrylate polymers
The research presented in this dissertation focused on the investigation of thermal properties in different polymer families. The study on polyimides and polyamides and involves backbone modifications (Chapters II-IV). Polyimides with significantly enhanced solubility with retention of high T g and thermal stability were synthesized from highly substituted diamines incorporating multiple ortho-methyl or ethyl groups hindering C-N bond rotation. Novel bis(ether amine)s which combine flexible ether linkages and multiple ortho-methyl or t-butyl substitution at the ether sites incorporated into polyimides and polyamides resulted in slight enhancement of solubility, high T g and thermal stability. Polyimides from a novel bis(ether amine) containing a non-aromatic cardo-cyclohexene unit with no ortho-substitution were prepared. These polyimides showed improved solubility with acceptably high Tg and good thermal stability. In the methacrylate research (Chapter V), the spacer effect in the thermal properties of adamantyl-substituted methacrylates and their copolymers was investigated. The homopolymer of novel 1-adamantylmethyl methacrylate (AdMMA), showed high Tg with a slight loss of thermal stability with respect to those containing direct adamantane attachment. Syrene-AdMMA copolymers showed incremental increase in copolymer Tg (0.88°C/mol) with increasing content of AdMMA. Slightly higher reactivity of AdMMA over styrene was observed. Novel dehydroalanine (DHA) monomers (incorporating methyl, benzyl or adamantyl groups), their homo- and MMA-copolymers were synthesized in the research addressed in Chapter VI. Polymer properties displayed effects of the substituent proximity to the backbone, flexibility of the spacers and the type of functionalities (amide versus ester) as well as synergism between substituent effect and hydrogen bonding. Copolymer T g 's increased with increasing DHA-monomer content. Dramatically higher radical reactivity of DHA-monomers over MMA was observed.