Polyimides based on 3,5-diaminobenzonitrile: Correlation of different properties with various dianhydride monomers

Abstract

A series of polyimides (PIs) was synthesized by reacting a nitrile-containing aromatic diamine, 3,5-diaminobenzonitrile, with various dianhydrides to yield poly(amic acid)s that were then cyclized to yield PIs by a thermal imidization method. The samples were characterized using thermal analysis, tensile testing, optical transparency analysis, and gas permeability analysis. The cast films exhibited good thermal stability with glass transition temperatures of 204-243 degrees C and none exhibited significant decomposition at temperatures below 480 degrees C. These PI films showed coefficient of thermal expansion values in the range 41.68-106.16 ppm/degrees C. The oxygen transmission rate values of the films containing various dianhydride monomers were in the range 0.93-27.40 cc m(-2) day(-1). The PI films containing various dianhydride monomers showed tensile strengths of 47-128 MPa, initial moduli of 2.16-3.23, and elongations at break of 1-7%. Moreover, the PI films possessed a transmittance of 58-82% at 500 nm and had a yellowish color with a yellow index of 12.17-59.61.