LC-polyimides—14. Thermotropic copoly (ester-imide)s derived from N-(3′-hydroxyphenyl) trimellitimide and 4-hydroxybenzoic acid or 6-hydroxy-2-naphthoic acid

Abstract

Starting from N-(3′-acetoxyphenyl)trimellitimide a semicrystalline homopoly(ester-imide) was prepared by thermal polycondensation in bulk. Furthermore, a series of copoly(ester-imide)s was prepared by cocondensation with 4-acetoxybenzoic acid (4-HBA). With a 4-HBA content up to 40 mol% the melt of these copoly(ester-imide)s is isotropic whereas with ⩾ 50 mol% of 4-HBA a nematic melt is obtained. With ⩾60 mol% of 4-HBA these thermotropic copoly(ester-imide)s are semicrystalline. An analogous series of copoly(ester-imide)s was prepared from 6-hydroxy-2-naphthoic acid (HNA). Also these copoly(ester-imide)s form a nematic melt with >40 mol% HNA units, but the tendency to crystallize is poor. Both series of copoly(ester-imide)s have in common that the glass-transition temperatures ( T g) are high and vary little with the molar composition. Four copoly(ester-imide)s were prepared from HNA and N-(4′-hydroxyphenyl)trimellitimide or N-(4′-carboxy-phenyl)4-hydroxyphthalimide. These copoly(esterimide)s are high melting 〈400 2〉, thermotropic materials.