New poly(amide‐imide) syntheses, 4 Poly(amide‐imide)s derived from 2,5‐bis(4‐aminophenyl)‐3,4‐diphenylthiophene and various bis(trimellitimide)s

Fifteen bis(trimellitimide)s 2a–o were prepared by condensation of the corresponding aliphatic or aromatic diamines with trimellitic anhydride. A series of structurally new poly(amideimide)s were synthesized by the direct polycondensation of these bis(strimellitimide)s with 2,5‐bis(4‐aminophenyl)‐3,4‐diphenylthiophene using triphenyl phosphite and pyridine as condensing agents in N‐methyl‐2‐pyrrolidone (NMP). The resultant poly(amide‐imide)s have inherent viscosities in the range between 0,72 and 2,73 dL/g at 30°C in N,N‐dimethylacetamide (cf. Tab. 2). The polymers are amorphous and readily soluble in polar aprotic solvents such as N,N‐dimethylacetamide (DMAc) and NMP. Transparent and tough films can be cast from their solutions. Most aliphatic‐aromatic poly(amide‐imide)s show a glass transition in the range between 203 and 242°C in their differential scanning calorimetry (DSC) traces, whereas the wholly aromatic poly(amide‐imide)s show no discernible transition before decomposition. The thermal stability of the polymers was evaluated by thermogravimetry which showed the 10% weight‐loss temperatures in the range between 414 and 459°C in air and between 451 and 578°C in a nitrogen atmosphere for the aliphatic‐aromatic poly(amide‐imide)s and above 500°C in both air and nitrogen atmosphere for the wholly aromatic poly(amide‐imide)s.