New kinds of phenylethynyl-terminated polyimide oligomers with low viscosity and good hydrolytic stability

In continuing studies to develop low melt viscosity phenylethynyl end-capped imide oligomers for aerospace applications, new kinds of all-aromatic phenylethynyl-terminated imide oligomers were prepared by the reaction of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) or biphenylenetetracarboxylic dianhydride (s-BPDA) with 2,5-bis(4-aminophenoxy)-biphenyl (p-TPEQ) and 4-phenylethynylphthalic anhydride (PEPA) or 4-(1-phenylethynyl)1,8-naphthalic anhydride (PENA). The oligomers bearing pendant phenyl groups exhibit much lower melt viscosities at low temperatures, and thus provide wide processing window. The thermal curing process of the oligomers was investigated with DSC. The tensile and thermal properties of the cured films were evaluated. Oligomers derived from PENA cured at lower temperatures and the corresponding cured polymers show better hydrolytic stability than those of PEPA. Results showed that the utilization of diamine monomer (p-TPEQ) can improve the processability and solubility of phenylethynyl-terminated imide oligomers without sacrificing their thermo-oxidative stability.