Novel regular network wholly aromatic polyester and polyamide films

Abstract

Novel regular network wholly aromatic polyester and polyamide films were prepared from trimesic acid (Y) and aromatic diols and aromatic diamines. Prepolymers prepared by melt polycondensation were cast from dimethylformamide solution and post-polymerized at various elevated temperatures and times to form networks. The resultant films were insoluble in any organic solvents. Heat distortion temperature T h of both polyester and polyamide films increased with increasing post-polymerization temperature and time. Polyester films of OY, prepared from Y and 4,4′-dihydroxybiphenyl ether (O) post-polymerized at 290°C for 18 h, and of BY, prepared from Y and 4,4′-dihydroxybiphenyl (B) post-polymerized at 340°C for 2 h, showed the highest T h (430°C) of the polyester films studied. Polyamide films of O′Y, prepared from Y and 4,4′-diaminobiphenyl ether (O′) post-polymerized at 350°C for 2 h, had the highest T h (444°C) of the polyamide films studied. The degree of reaction, a measure of network formation, increased with increasing post-polymerization time. X-ray diffraction patterns of these network polymer films exhibited broad but distinct diffraction peaks, suggesting the formation of some ordered structure owing to the regular network formed by symmetrical trimesic acid moiety. The density of polyester films decreased and that of polyamide films increased with increasing post-polymerization time. These network polymers had tensile strengths and Young's moduli lower than the network polyester film of 2GY prepared from Y and ethylene glycol (2G). Temperature profiles of both thermomechanical analysis and thermogravimetry of polyamide films exhibited higher thermal resistance than polyester films, suggesting the formation of a carbonized structure at higher temperature.