Synthesis and characterization of aromatic polyamides and polyimides from trimethyl- and di- t-butylhydroquinone-based ether-linked diamines

Abstract

1,4-Bis(4-aminophenoxy)trimethylbenzene ( 3a) and 1,4-bis(4-aminophenoxy)-2,5-di- t-butylbenzene ( 3b) were synthesized in two steps from the hydroquinones via nucleophilic aromatic substitution and catalytic reduction. Aromatic polyamides were synthesized from these diamines by direct polycondensation with various diacid chlorides or by reaction with diacids, triphenyl phosphite and pyridine in N-methyl-2-pyrrolidinone (NMP). Aromatic polyimides were synthesized from the trimethyl monomer using commercial dianhydrides in two-step polycondensations. Characterization of polymers was accomplished by 1H n.m.r., 13C n.m.r., FTi.r., d.s.c. and t.g.a. Intrinsic viscosities of polyamides were between 0.30 and 0.73 dl g −1 in NMP for the trimethyl polymers and between 0.57 and 1.47 dl g −1 in 5% LiCl/NMP for the di- t-butyl polyamides. Viscosities of the poly(amic acid)s ranged from 0.45 to 0.85 dl g −1. Polyamides displayed T g values of 237–305°C and 5% weight loss values above 402°C in N 2. T g values of polyimides varied between 235 and 300°C, with 5% weight loss values above 435°C in N 2. Most polyimides were only soluble in H 2SO 4, while polyamides were soluble in polar aprotics such as NMP, N, N-dimethylacetamide and dimethyl sulfoxide.