Fluorescence characterization of model compounds for cyanate monomers, cure intermediates, and cure product

To elucidate the origin of the spectral changes observed in fluorescence emission during the cure reaction of a bisphenol A dicyanate ester monomer, seven model compounds representing monomers, impurities, cure intermediates, and cure product were investigated. Fluorescence spectroscopic characterization indicate that aryl cyanate esters, aryl carbamate, and aryl iminocarbonate compounds exhibit a characteristic fluorescence emission at around 300 nm from substituted benzene rings. However, in the model cure product, tricumylphenoxyl-s-triazine, the emission was observed near 420 nm, which is similar to the fluorescence observed during cure of cyanate ester monomer. The soluble oligomer in the solid state and the trimer from a monofunctional cyanate monomer also exhibit the observed fluorescence emission near 420 nm. It was concluded that the origin of the observed fluorescence during resin cure is mainly due to the cross-linker which is similar to tricumphenoxyl-s-triazine.