Charge-transfer complexes of pyridinium ions and methyl- and methoxy-substituted benzenes as photoinitiators for the cationic polymerization of cyclohexene oxide and related compounds

The cationic photopolymerization of cyclohexene oxide and 4-vinylcyclohexene dioxide was achieved by using charge-transfer (CT) complexes of pyridinium salts and aromatic electron donors (hexamethylbenzene and 1,2,4-trimethoxybenzene) as initiators. Irradiation of the CT complexes with light of relatively long wavelength produces radical cations of the aromatic electron donors capable of initiating cationic polymerization. N-Vinylcarbazole and n-butyl vinyl ether are spontaneously polymerized in CH₂Cl₂ solution in the dark at room temperature upon addition of the CT complexes mentioned above. The molar extinction coefficients ε_ct and equilibrium constants K_ct of the CT complexes have been determined.