Acridinium salt mediated photopolymerization of acrylates and methacrylates with dihydropyridine-iodonium salt combinations

Abstract

In a photoassisted reaction, by exposure of 9-phenyl-10-methylacridinium salt to blue light ( λ = 405, 436 or 460 nm) in the presence of a 1,4-dihydropyridine derivative as electron donor and diphenyliodonium salt as electron acceptor, phenyl radicals are formed. The phenyl radicals initiate the polymerization of methyl methacrylate in acetonitrile solutions or of bulk multifunctional acrylate monomers usually used in industrial formulations. With bisphenol-A-diglycidylether diacrylate the utilization of the electron donor is not necessary, because this monomer can function as coinitiator in such formulations. The phenoxy molecular structure of the monomer gives rise to an electron transfer reaction responsible for the formation of initiating radicals. Other dyes can also be used as light-absorbing components in such ternary systems. Systems having tetrabromomethane instead of the iodonium salt as electron acceptors exhibit the same polymerization efficiency.