Synthesis and properties of new soluble poly(amide–imide–imide)s based on tetraimide-dicarboxylic acid condensed from ODPA, BAPP and p-ABA, and various aromatic diamines

A new-type of tetraimide-dicarboxylic acid (I) was synthesized starting from ring-opening addition of p-aminobenzoic acid (p-ABA), 4,4′-oxydiphthalic anhydride (ODPA) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) at a 2:2:1 molar ratio in N-methyl-2-pyrrolidone (NMP), followed by cyclodehydration to the diacid I. A series of poly(amide–imide–imide)s (IIIa–i) with inherent viscosities of 0.82–1.20 dl g−1 was prepared by triphenyl phosphite-activated polycondensation from the tetraimide-diacid (I) with various aromatic diamines (IIa–i) in a medium consisting of NMP, pyridine, and calcium chloride. Most of the polymers were readily soluble in a variety of organic solvents such as NMP, N,N-dimethyl acetamide (DMAc), dimethyl sulfoxide (DMSO), and even in less polar m-cresol. In comparison with corresponding poly(amide–imide)s (IVa–i), the solubilities of poly(amide–imide–imide)s (IIIa–i) were largely improved. Most of the polymers (III) afforded tough, transparent, and flexible films, which had tensile strengths ranging from 96 to 107 MPa, elongations at break from 9 to 16%, and initial moduli from 2.0 to 2.3 GPa. The glass transition temperatures of polymers recorded at 257–278 °C. They had 10% weight loss temperature above 540 °C and left more than 46% residue even at 800 °C in nitrogen.