Thiol−Ene Free-Radical and Vinyl Ether Cationic Hybrid Photopolymerization

The photopolymerization kinetics of mixtures containing a trithiol and a trivinyl ether (in different molar ratios) with a cationic photoinitiator were investigated by real-time infrared and real-time rheology. Using this combination of real-time methods to follow both chemical conversion and rheological property development, a clear picture of physical property development during the complete polymerization process is obtained. This represents the first example of a thiol−ene radical/ene cationic two-step hybrid photopolymerization process in which thiol copolymerizes with vinyl ether functional groups in a rapid radical step growth process followed by vinyl ether cationic homopolymerization. The sequential thiol−vinyl ether copolymerization and the vinyl ether cationic polymerization result in cross-linked networks with thermal and mechanical properties that are combinations of each system.