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Curing bis(maleimide)/diallylbisphenol A (BMI/DABPA) results in the formation of a high-temperature thermoset resin. FT-IR, fluorescence, and UV-reflectance spectroscopy were used to investigate the cure behavior of this material under three different cure schedules. Fluorescence signals were quenched before curing due to the BMI component but increased and eventually leveled off as cure time increased. The largest fluorescence intensity increases occurred after 80% of the phenylmaleimide units were converted to phenylsuccinimide. Fluorescence signals were observed in both short-wavelength and long-wavelength regions. Model compound studies indicated that the phenolic portion of the BMI/DABPA resin has a higher quantum yield for fluorescence at a shorter wavelength than phenylsuccinimide derivatives. Therefore, fluorescence emission observed near 356 nm during curing is attributed to phenolic structures. FT-IR was used to quantify the extent of succinimide formation and to identify cross-linking processes which occurred during high temperature curing (250−260 °C). High-temperature curing processes were also identified by UV-reflection spectroscopy. Various reaction pathways are discussed in terms of their consistency with the spectroscopic data.

Curing bis(maleimide) (BMI) with diallylbisphenol A (DABPA) results in the formation of a high-performance thermoset resin. A variety of reactions in which maleimide units are converted to succinimide moieties have been proposed. In order to make spectral assignments for the fluorescence behavior observed during the cure of BMI/DABPA resin and to assess the likelihood that certain types of reactions take place during resin cure, several succinimide model compounds were synthesized from N-phenylmaleimide (NPM) and characterized. These model compounds gave fluorescence signals which were red-shifted by 40 nm or more from the emission maximum in DABPA resin, while no fluorescence was observed from the BMI. The BMI was found to quench the fluorescence from DABPA and a Stern−Volmer quenching constant was determined for this pair. Relative fluorescence quantum yields were determined for the model compounds. The DABPA resin component was found to have the highest quantum yield and is likely to be responsible for most of the fluorescence near 356 nm when the resin is excited near 280 nm. A succinimide derivative which arises from a Diels−Alder−Ene reaction sequence was found to have a higher quantum yield than other succinimides which were investigated. This type of structure might be responsible for most of the fluorescence observed in the long wavelength regions. Fluorescence peak shapes and peak positions were found to have a concentration dependence.