Photoinduced free radical promoted cationic polymerization 40 years after its discovery

This perspective article is prepared in the memory of Anthony Ledwith who discovered Free Radical Promoted Cationic Polymerization (FRPCP) as a versatile photoinitiating system for cationic polymerization about four decades ago. Mechanistically, distinct modes for the photochemical formation of electron donor radicals in the UV, Vis and NIR range that can be oxidized to reactive cations to initiate the cationic polymerization of oxiranes and vinyl monomers are discussed. The dual polymerization strategies that have been applied to combine FRPCP with the other modes of polymerization processes are presented.