The effect of synthesis route and ortho-position functional group on thermally rearranged polymer thermal and transport properties
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This dissertation discusses the effect of synthesis route and ortho-position group on the thermal and transport properties of thermally rearranged polymers. Thermally rearranged polymers are polybenzoxazoles formed via the solid state rearrangement of ortho-functional polyimides. In this study, polymers were derived from 3,3'-dihydroxy-4,4'-diamino-biphenyl and 2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (HAB-6FDA). These HAB-6FDA polymers were synthesized using chemical and thermal imidization, and hydroxyl, acetate, propanoate, or pivalate ortho-position groups were considered. In these polymers, gas permeability increases as a function of conversion for all samples. The polyimide synthesis route does not affect the thermal or transport properties. However, the precursor ortho-position group strongly influences the thermal and transport properties of TR polymers. Additionally, it was determined that an increase in gas diffusivity was the primary cause of increased permeability as a function of thermal rearrangement.