Synthesis and characterization of new soluble cardo poly(amide–imide)s derived from 2,2-bis[4-(4-trimellitimidophenoxy)phenyl]norbornane

A series of new soluble poly(amide–imide)s were prepared from the diimide-dicarboxylic acid, 2,2-bis[4-(4-trimellitimidophenoxy)phenyl]norbornane, and various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone containing CaCl2, using triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 1.01–1.42 dL g−1. Gel permeation chromatography (GPC) of the polymers showed number-average and weight-average molecular weight up to 67,300 and 118,000, respectively. The poly(amide–imide)s were amorphous and were readily soluble in various solvents such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), pyridine, cyclohexanone and tetrahydrofuran. Tough and flexible films were obtained by casting their DMAc solution. The films had tensile strength of 89–110 MPa and a tensile modulus range of 1.8–2.2 GPa. The glass transition temperatures of the polymers were determined by DSC method and they were in the range of 265–295 °C. The polymers were fairly stable up to a temperature around or above 450 °C, and lose 10% weight in the range of 472–504 °C and 490–520 °C in nitrogen and air, respectively.