Polyimides, 1. Studies on the thermal curing of imide model compound with tricyclic structure by nuclear magnetic resonance and mass spectra

A model imide with a tricyclic structure was synthesized by reacting 3-phenyltricyclo[6.2.2.0^2,7]-2,11-dodecadiene-5,6 : 9,10-tetracarboxylic dianhydride with aniline. The thermogravimetry curve showed that it degraded at about 300°C, and its differential scanning calorimetry curve was found to be similar to that of its corresponding polyimides. The thermal curing of this model imide was studied in detail. A curing mechanism was proposed based on the analysis of the cured product using NMR and mass spectroscopy. The results show that the curing mechanism started with a reverse Diels-Alder reaction, forming an intermediate which either dehydrogenated or further decomposed into 1,1-diphenylethylene, and N-phenylsuccinimide. The 1,1-diphenylethylene and N-phenylsuccinimide would either polymerize or become hydrogenated to form 1,1-diphenylethane and N-phenylsuccinimide, respectively.