Colorless full-alicyclic polyimides with low dielectric constant

Abstract

The fully alicyclic polyimides were prepared by a 2-step polycondensation of 2,5(6)-bis(aminomethyl)bicyclo[2.2.1]heptane with cycloaliphatic dianhydrides such as bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic dianhydride. These polyimides possessed a 5% weight-loss temperature range of 422-459°C in N2, and 411-416°C in air. The polyimides had the Tg's over 200°C, especially those of polyalicyclic polyimides were over 250°C. The free-standing polyimide films exhibited cutoffs at a wavelength shorter than 235 nm, and are colorless. The averaged refractive indices were 1.52-1.54 and the optical anisotropies, birefringencies, were nearly zero. The dielectric constants that were evaluated from the refractive index were 2.55-2.73.