Preparation of poly(amide‐imide)s by direct polycondensation with triphenyl phosphite, 3. Poly(amide‐imide)s based on bis(trimellitimide)s

Abstract

Abstract Six dicarboxylic acids ( 1a–f ) were prepared from trimellitic anhydride and 4,4′‐oxydianiline, 4,4′‐methylenedianiline, 4,4′‐sulfonyldianiline, benzidine, 1,6‐hexamethylenediamine, and 4,4′‐methylenedicyclohexylamine. These diacids were condensed directly with various aromatic diamines using triphenyl phosphite in 1‐methyl‐2‐pyrrolidone/pyridine solution in the presence of calcium chloride. The inherent viscosity of the polymers is affected by the nature of the diamine and the solubility of the resulting polymers in the reaction media. The highest η inh ‐value of a poly(amide‐imide) obtained was 1,41 dl/g (in N , N ‐dimethylacetamide/5% LiCl at 30°C). Among the polymers, the wholly aromatic ones show better solubility, higher glass transition temperatures, and higher thermostability than the aliphatic‐aromatic ones. Well‐defined melting points ( T m ) of most wholly aromatic poly(amide‐imide)s were not obtained by differential scanning calorimetry (DSC); however, some poly(amide‐imide)s containing aliphatic chains showed clear T m in the first DSC heating traces. Measurements of wide‐angle X‐ray diffraction revealed that those polymers containing biphenyl or linear hexamethylene groups are partially crystalline. Flexible films with excellent tensile properties were cast from N , N ‐dimethylacetamide solutions of most of the wholly aromatic poly(amide‐imide)s.