Aromatic polyamide-imides as materials for membranes. I. Synthesis and characterization

Diamine amic acids were synthesized by reacting aromatic diamines with pyromellitic dianhydride in dimethylacetamide/dioxane. High molecular weight polyamide‐amic acids were prepared by low‐temperature solution polymerization of diamine amic acids with isophthaloyl chloride in dimethylacetamide. The cyclodehydration of polyamide‐amic acids to the corresponding polyamide–imides was accomplished by heating the cast films at 175°C for 3 h. The polyamide–imides were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N‐methyl‐2‐pyrrolidone and could be cast into tough and flexible films. They were characterized by elemental analyses, inherent viscosities, IR, and 1H‐NMR spectra. The glass transition temperatures of polyamide–imides were determined by differential scanning calorimetry. The thermal stabilities of the polymers were measured by thermogravimetric analyses in air. © 1995 John Wiley & Sons, Inc.