Characterization of High-Performance Polyimides Containing the Bicyclo[2.2.2]oct-7-ene Ring System

ABSTRACT Polyamic acids and polyimides were synthesized by the polycondensation of bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride with 1,4-phenylenediamine, 1,3-phenylenediamine, 3,3′-dimethyl-4,4′-diaminobiphenyl diamine (o-tolidine), and 2,2′-bis(trifluoromethyl)benzidine. Thermogravimetric analysis indicates that the corresponding polyamic acids and polyimides were stable up to approximately 450°C under argon and air. Thermal and thermo-oxidative stability was higher for polyimides derived from disubstituted biphenyl moieties (CF3 or CH3) and bicyclic ring systems. The polymers exhibited enhanced solubility in organic solvents such as dimethyl sulfoxide, N,N-dimethylacetamide, and N,N-dimethylformamide. The polymers with high aromatic character tend to exhibit decreased solubility. X-ray data indicated that the polyamic acids are amorphous.