Origin of fluorescence in the cure reaction of aromatic dicyanates

The origin of fluorescence in the cure reaction of aromatic dicyanates was thoroughly investigated using a fluorescence spectrophotometer and a UV–Vis spectrophotometer. Some highly pure cyanates or dicyanates, such as 4-cumylphenyl cyanate (CPCy), 2,2-bispheny cyanate (BIPCy) and tricumylphenoxy-s-triazine (TCT), were successfully synthesized for the investigation of the fluorescence origin. Fluorescence characterizations of the purchased bisphenol A dicyanate (BADCy) and the synthesized 2,2-bispheny cyanate (BIPCy) during the curing process were utilized to explain the self-quenching effect. The purchased 2,4,6-triphenoxy-1,3,5-triazine (TPOT), 2,4,6-triphenyl-1,3,5-triazine (TPT) and the synthesized TCT, all of which possess a single s-triazine ring, were used as model compounds to pinpoint the exact origin of fluorescence. The results demonstrate that the origin of fluorescence in the curing process of aromatic dicyanates does neither arise from the s-triazine ring itself nor the intermolecular π-stacking, but from the substitution groups. The s-triazine ring in association with the substitution groups determined the characteristics of the fluorescence.