Intrinsic fluorescence during the reactions between methylene 4,4‘-diphenyl diisocyanate (MDI) and 1-butanol or hydroxy-terminated poly(propylene oxide) was investigated to characterize a model urethane reaction and polyurethane formation both in dilute solution and in bulk. Fluorescence intensity was found to increase about 87 times when MDI was converted to diurethane, with the emission maximum around 315 nm. The rate constants and the activation energies for the model reaction and polyurethane formation were obtained from the fluorescence results and compared with the IR results. The correlation between the fluorescence intensity and the extent of the reaction determined by IR has been established.

The kinetic studies of the crosslinking reaction of a nadic end‐capped imide model compound, N,N′‐(oxydi‐3,4′‐phenylene) bis(5‐norbornene‐2,3‐dicarboximide), a bisnadimide, in thermal and microwave processes were investigated. The conversion of the endo isomer to exo isomer proceeds at a much lower temperature than the crosslinking reaction. The crosslinking reaction was monitored by the combined decrease in the infrared absorptions of the endo and exo isomers at 840 and 780 cm−1, respectively. The decrease in the concentration of starting materials follows first‐order kinetics in the thermal and microwave processes. At the same temperatures (230 or 280°C), the crosslinking reaction proceeds at about 10 times faster in the microwave process than in the thermal process. Solid‐state 13C‐NMR showed no significant loss in C=C double bond resonance in the cured products by comparison with the starting material. This study provides direct evidence that the microwave process may be an efficient method to cure nadic end‐capped polyimides. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2653–2665, 1998