Thermotropic polyesters: synthesis and properties of t-butyl-substituted poly(4-oxybenzoate)s

Abstract

Two series of novel t-butyl-substituted copolyesters, poly(3- t-butyl-4-oxybenzoate- co-4-oxybenzoate)s and poly(3,5-di- t-butyl-4-oxybenzoate- co-4-oxybenzoate)s, have been synthesized. The former were prepared by the conventional transesterification reaction via an acetolysis route and the latter were made from or via a novel monomer, 3,5-di- t-butyl-4-hydroxybenzoyl chloride. These polymers were characterized by solution viscometry, infra-red spectroscopy, wide angle X-ray scattering, hot-stage polarizing microscopy and thermal analysis (d.s.c., t.g.a. and t.m.a.). Both poly(3- t-butyl-4-oxybenzoate) and poly(3,5-di- t-butyl-4-oxybenzoate) were semicrystalline and did not melt before decomposing, although they were easily soluble in conventional solvents. Of the monosubstituted copolymers, only the 50:50 composition melted at a temperature substantially below decomposition, forming a nematic mesophase, which makes this copolymer the most promising for processing. None of the disubstituted copolymers melted below its decomposition temperature.