Synthesis and Properties of Copolyimides Derived from Isometric Biphenyltetracarboxylic Dianhydrides (a-BPDA and i-BPDA) and Oxydiphthalic Dianhydride (ODPA) with 4,4’-Oxydianiline (4,4’-ODA)

Abstract

Two series of polyimides were prepared by thermal imidization of polyamide acid derived from 2,3,3’,4’-biphenyltetracarboxylic dianhydride (a-BPDA), 2,3,2’,3’-biphenyltetracarboxylic dianhydride (i-BPDA) or 3,3’,4,4’-oxydiphthalic dianhydride (ODPA) and 4,4’-oxydianiline (4,4’-ODA). The properties of copolyimides derived from a-BPDA and i-BPDA were compared with those of the copolyimides based on a-BPDA and ODPA. The glass transition temperature ( Tg) of the former copolyimides increased with an increase of the i-BPDA component, whereas Tg of the later copolyimides decreased with the increase of the ODPA component. The i-BPDA-based copolyimides had higher Tg and better solubility than the a-BPDA homopolyimide, while the ODPA based copolyimides had higher elongation at break. The tensile, dynamic mechanical properties and coefficient of thermal expansion of these copolyimides were characterized.