Cationic polymerization using mixed cationic photoinitiator systems

Photoinitiated cationic polymerization is useful wherever the lack of oxygen inhibition, low shrinkage and formation of polymers with good adhesion properties are essential. Rates and conversions for cationic polymerizations of epoxycyclohexylmethyl-epoxycyclohexane carboxylate (ECHC) with various cationic photoinitiators and their blends were compared. Glass-transition temperatures of polymers were determined by dynamic mechanical analysis. When photopolymerizations of ECHC with initiator blends were compared with single-initiator systems, strong synergies leading to high polymerization rates and conversions were discovered for blends of diaryliodonium hexafluoroantimonate (IA) with tolylcumyliodonium tetrakis(pentafluorophenyl)borate (IB), and cumenecyclopentadienyliron(II) hexafluorophosphate with IA and IB. Mechanisms responsible for the discovered synergies are proposed.