Can Quantum Chemistry Support Photoinitiator Research

Photoinitiators for radical polymerisations must induce a rather fast curing process. On the molecular level this means that they have to undergo an a-cleavage reaction with a high efficiency and the thus generated radicals have add to double bonds on a fast time scale. An acylphosphine-type photoinitiator is irradiated at an appropriate wavelength. It is transferred into an excited singlet state, then intersystem crossing leads to the formation of the excited triplet state. In the latter stage, the molecule undergoes a-cleavage and a radical pair (consisting of a benzoyl and phosphinoyl radical) is formed.