Three component ketocoumarin, amine, maleimide photoinitiator I

An N-substituted maleimide has been used in conjunction with ketocoumarins and a tertiary amine to initiate the polymerization of 1,6-hexanedioldiacrylate in both the UV (365/366 nm) and visible region (436 nm) of the electromagnetic spectrum. The rate of polymerization of three ketocoumarin/tertiary amine combinations are significantly increased by the addition of a N-substituted maleimide, presumably due to oxidation of the coumarin ketyl radical formed by interaction between the triplet state of the ketocoumarin and the tertiary amine.