Synthesis, characterization and thermal behaviour of poly(pyromellitimide-ester)s and (imide-urethane)s containing azobenzene units

Two new series of poly(pyromellitimide-ester)s and (imide-urethane)s were s ynthesized from N,N'-bis(omega-hydroxyalkyl)pyromellitimides (HAPMIs) with 4,4'-azobenzenedicarboxylic acid by melt polycondensation, and HAPMIs with 4,4'-azobenzenedicarboxylicacid azide by solution polycondensation, respect ively. The polymers were characterized by elemental analysis, IR,H-1 and C- 13 NMR and X-ray diffraction analysis. The d-spacings calculated for poly(i mide-ester)s show an odd-evert effect. The thermal stability and phase tran sition behaviour were studied by TGA, differential scanning calorimetry (DS C) and hot-stage optical polarized microscopy (HOPM). Poly(imide-ester)s sh ow higher T-g and T-m values than the corresponding poly(imide-urethane)s. T-g values decrease linearly as the number of methylene spacer increases, w hile T-m shows odd-even effect. Poly(imide-ester)s show higher thermal stab ility than the corresponding poly(imide-urethane)s, and in the git en serie s thermal stability decreases with an increase in the number of methylene s pacers. (C) 1998 Elsevier Science Ltd. All rights reserved.