Layer structures .7. Thermotropic poly(ester-imide)s based on trimellitic anhydride and branched diamino alkane spacers

Two new dicarboxylic acids were synthesized from trimellitic anhydride and 1,5-diamino-2-methylpentane or from a mixture of isomeric 1,6-diamino-trimethyl hexanes. These dicarboxylic acids were polycondensed either with the bisacetate of 2,6-dihydroxynaphthalene or with the bisacetate of 4,4'-dihydroxybiphenyl. D.s.c. measurements, WAXD powder patterns and optical microscopy revealed that all four poly(esterimide)s derived from 1,5-diamino-2-methylpentane still form a highly ordered, quasi crystalline smectic layer structure in the solid state, but a nematic phase in the molten state. The poly(ester-imide)s derived from the trimethyl substituted spacers only form a smectic glass in the solid state. This smectic glass is a frozen smectic-A phase in the case of 4a but may be a mixture of frozen smectic-C and smectic-A phases in the case of 4b (derived from 4,4'dihydroxybiphenyl). Upon heating above the glass-transition the layer structures gradually disappear with formation of a nematic phase. Due to this gradual change revealed by synchrotron radiation measurements no endothermic phase transition is detectable in the d.s.c. traces. (C) 1997 Elsevier Science Ltd.