Abstract: A photopolymerizable composition comprising at least one polymerizable ethylenically unsaturated material, for example, an ethylenically unsaturated monomer, and a photosensitive catalyst comprisingA. at least one photosensitizer having the structure ##STR1## where X is >C=O, >CR.sub.1 R.sub.2 or >CR.sub.3 OR.sub.4, especially >C=O, R.sub.1 to R.sub.4 and hydrogen or hydrocarbyl groups, n is 0 or 1, and the groups A are hydrocarbyl or substituted hydrocarbyl groups, the groups A being aromatic or substituted aromatic when n is 1 and X is >CR.sub.1 R.sub.2 and when n is 0, andB. at least one reducing agent, for example, an amine or a phosphine, capable of reducing the photosensitizer when the photosensitizer is in an excited state.

Abstract: Photopolymerizable compositions consisting essentially of at least one polymerizable ethylenically unsaturated material and a photosensitive catalyst comprisingA. from 0.5% to 5% by weight based on the ethylenically unsaturated material of at least one photosensitizer having the structure ##EQU1## wherein Ph is phenyl, halogen-substituted phenyl, phenylene or halogen-substituted phenylene and A is a cyclic hydrocarbyl group, a halogen-substituted cyclic hydrocarbyl group or a group of the formula ##EQU2## where X and Y each is hydrogen, a hydrocarbyl or a halogen-substituted hydrocarbyl group, andB. from 1 to 5% by weight based on the ethylenically unsaturated material of a reducing agent capable of reducing the photosensitizer when the photosensitizer is in an excited state.Also described is a process of preparing polymeric materials by irradiating the foregoing polymerizable composition at a wavelength capable of exciting the photosensitizer to an excited state.