Low Temperature Film-fabrication of Hardly Soluble Alicyclic Polyimides with High T_g by a Combined Chemical and Thermal Imidization Method

Abstract

The alicyclic dianhydride having cyclopentanone bis-spironorbornane structure (CpODA) was polycondensated with aromatic diamines at room temperature to give poly(amic acid)s having an inherent viscosity (η_inh) range of 1.3-0.54 dL/g. The poly(amic acid)s were imidized by three methods. The imidization ratio of PI(CpODA+3,4’-DDE) reached 100% at 200 °C using a combined chemical and thermal imidization method. All the polyimide films possessed excellent thermal stability and most of the polyimides had Tg’s over 330 °C. The CTE value of thermally imidized PI(CpODA+4,4’-DABA) was as low as 15 ppm/K. The polyimide films exhibited λ_cut-off’s shorter than 336 nm, and the T_vis value of each polyimide film was over 85%. Especially, PI(CpODA+3,4’-DDE) prepared by a combined chemical and thermal method had outstanding optical properties (T_vis:88 %, λ_cut-off’s:278 nm) due to the low temperature film-fabrication.