Syntheses and Characterizations of Colorless and Transparent Poly(amide imide) Copolymer

Abstract

N,N'-[2,2'-bis(trifluoromethyl)-4,4'-biphenyleneibis(4-aminobenzamide) (TFAB) was synthesized from 4nitrobenzoyl chloride and 2,2'-bis(trifluoromethyl)benzidine (TFB). The obtained TFAB, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 4,4'-biphthalic anhydride (BPA) were used to synthesize polyimide copolymers (Co-PIs) containing amide groups. Flexible and tough Co -PI films were prepared from poly(amic acid) (PAA) through solution -casting using chemical and thermal imidization methods. The thermomechanical properties and optical transparency of the Co -PI films with various BPA monomer contents were investigated. The coefficients of thermal expansions (CTEs) of the Co -PI films were improved linearly with increasing BPA content. However, their optical transparency was found to worsen with increasing BPA content.