Microporous Thioxanthone Polymers as Heterogeneous Photoinitiators for Visible Light Induced Free Radical and Cationic Polymerizations

Conjugated microporous polymeric networks possessing thioxanthone groups were reported to initiate free radical and cationic polymerizations of vinyl monomers and cyclic ethers, respectively, under visible light irradiation. These new classes of Type II macrophotoinitiators with high porosity having large BET surface area of 500-750 m(2) g(-1) were prepared through different cross-coupling processes. Polymerizations are successfully achieved in conjugation with several co-initiators benefiting from hydrogen abstraction or electron transfer reactions stimulated by either visible light or natural sunlight irradiation. Photopolymerizations conducted by using knitted photoinitiators show better conversion and rate of polymerization than those obtained via Sonogashira-Hagihara coupling. The heterogeneous nature of the photoinitiators makes them easily separable from the media and more importantly reusable for further polymerizations while retaining the photocatalytic activity.