Universal Group 14 Free Radical Photoinitiators for Vinylidene Fluoride, Styrene, Methyl Methacrylate, Vinyl Acetate, and Butadiene

Group 14 (Mt = Sn, Ge, Pb) R 3 MtX, R 4 Mt, and R 6 Mt 2 complexes (R = alkyl, aryl; X = H, halide, etc.) are introduced as novel, universal, visible and black light bulb (BLB)/UV photoinitiators for free radical photopolymerization of alkenes, including vinylidene fluoride (VDF), vinyl acetate, methyl methacrylate, styrene, and butadiene. A comprehensive solvent, ligand and metal comparison for VDF indicates progressively faster BLB photopolymerizations in acetonitrile (ACN) ∼ dimethylacetamide (DMAc) < dimethyl sulfoxide (DMSO) < butanone < propylene carbonate < acetic anhydride ∼ cyclohexanone < dimethyl carbonate and especially in the photosensitizing acetone, where Me 2 SnI 2 ∼ Ph 3 SnI ∼ Bu 3 Sn–N 3 ∼ Bu 3 Sn–CH 2 –CH═CH 2 ≪ Bu 3 Sn–S–SnBu 3 < Ph 4 Ge < Ph 6 Pb 2 < Bu 3 Sn–I < Bu 4 Sn < Ph 6 Sn 2 < Bu 3 Sn–Br < Ph 6 Ge 2 < Oct 4 Sn < Bu 4 Ge < Bu 3 Sn–Cl < Ph 4 Pb < Bu 3 Sn–H ≪ Bu 6 Sn 2 ≪ Me 6 Sn 2 and where M n is controlled by solvent chain transfer. Photoinitiation results from a combination of R 3 Mt·, R·, and solvent (S·, e.g., CH 3 –CO–CH 2 ·) radicals, where R 6 Sn 2 (R = Me, Ph) initiates as R 3 Sn·, all Bu derivatives, as both Bu 3 Sn· and Bu·, and Ph 4 Mt and Ph 6 Mt 2 (Ge, Pb), only indirectly via S·. Interestingly, while R 3 Sn–CH 2 –CF 2 -poly(vinylidene fluoride) (PVDF) eliminates R 3 SnF to afford CH 2 ═CF–PVDF macromonomers, nonfluorinated alkenes are initiated even in bulk under visible light and do not undergo R 3 SnH elimination.