Alternate poly(amide-imide)s based on 1,4- and 1,3-bis(4-trimellitimido)benzene and their mixtures

several series of alternate poly(amide-imide)s [P(A-alt-I)s] were synthesiz ed by aromatic dicarboxylic acid (I-p or I-m), which was prepared by the co ndensation of p-phenylenediamine (or m-phenylenediamine), trimellitic anhyd ride, and various aromatic diamines by means of direct polycondensation. A diimide-diacid (I-p) with a p-phenylene group was used to synthesize P(A-al t-I)s III, and P(A-alt-I)s IV were synthesized by a diimide-diacid (I-m) pr epared from m-phenylenediamine. Another series of P(A-alt-I)s V was synthes ized from both I-p and I-m (1/1 mole) with various diamines. Polymers of se ries III have low inherent viscosities and limited solubility, but polymers of series IV have high degrees of polymerization. Series V copolycondensat ed from I-p and I-m has improved solubility and degrees of polymerization r elative to series III. The degree of crystallinity was found to be III > V > IV. Glass transition temperatures for most of series III were not observe d below 400 degrees C, and those of series IV and V were in the range of 23 8 similar to 325 degrees C and 262 similar to 328 degrees C, respectively. The 10% weight loss temperatures in nitrogen or in air of these three serie s are all in the range of 482-582 degrees C. Because series V has limited s olubility for casting into films from DMAc solutions, two diamines were sel ected to synthesize series VI by changing the I-p/I-m ratio. Solubility was improved when the content of I-p in diimide-diacid was less than 15%, and the degree of crystallinity reduced as the content of I-p in diimide-diacid decreased. Polymers containing a few I-p showed an increase in the initial modulus.