Thermal Durability Improvement in Transparency of Alicyclic Polyimide by Capping Terminal Amino Groups

Abstract

The alicyclic dianhydride (CpODA) was polycondensated with an aromatic diamine (4,4'-DDE) at room temperature. The poly(amic acid)s gave flexible and tough films by a thermal imidization method in the presence or the absence of acetic anhydride (Ac₂O). The resulting polyimide films were absolutely colorless. These polyimide films were reheated in the air at 300 ^oC and 350 ^oC for each 0.5 h. The thermal durability in transparency was extremely improved by adding Ac₂O and the effect was increased as an increase in the amount of Ac₂O. It was tried to prepare colorless alicyclic polyimide films in the air by thermal imidization. Several kinds of acylation reagents were used for end-capping. All the polyimide films prepared by thermal imidization in the air at 350 ^oC took brown color. However, it is found that two carboxylic anhydrides, Ac₂O and TFAA, showed a transparency improvement effect of alicyclic polyimide films even on the thermal imidization in the air.