Colorless, heat resistant polyimide films derived from 2,3,3′,4′-biphenyltetracarboxylic dianhydride

Abstract

The development of high performance colorless polyimide (PI) films is one of the targets of PI chemistry, since heat resistant colorless PI films are key materials for reliable plastic substrates in image display devices. In the present work, 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA) was used to polymerize with diamines to afford a series of PI, as shown in Scheme 1. Due to the fully aromatic composition, the films displayed high thermal decomposition temperatures (T5%). PI-FDA and PI-FFDA had similar glass transition temperatures (Tg) around 425°C, and much higher than that of PI-TFMB. PI-TFMB and PI-FFDA showed a transparent and colorless feature, with high transparency at 400nm (T400). Coefficients of thermal expansion (CTE) were found around 55ppm.°C−1 for the series of PI films, larger than the requirement of flexible substrate applications, which could be attributed to the distorted chain structure derived from the a-BPDA component.