A Reappraisal of Camphorquinone-amines Photoinitaiting Systems for Polymerization of Multifunctional Monomers

The intention of this paper is to discuss in some detail factors which determine camphorquinone (CQ)Iamine (AMH) photoinitiated polymerization. Emphasis is placed on the rate and course of radical reactions. CO can photoinitiate polymerization itself, however, at low speed and poor efficiency. In order to accelerate the photopolymerization, amines as co-initiators are commonly
used. Amine radicals formed initiate polymerization reactions. An extremely important criterion for the efficient polymerization is that the photoinitiator system CQ/AMH system, or any of its photofragments, must not function as chain transfer or terminating agents. Aliphatic amines with 2 groups reacts as retardants of polymerization, whereas with ) as efficient co-initiators.
Most of aromatic amines are also efficient co-initiators. Two mechanisms; Hatom abstraction and electron-proton transfer may participate in the CQ/AMH photogeneration of reactive amine radicals. The activity of amines as coinitiators depends on many factors such as their structure, capability of quenching of the excited triplet state of CQ, susceptibility of the formation of
charge-transfer complexes (CT-complexes) and/or contact ion pair complexes (CIP-complexes) with CO, and their oxidazibility. Depending on the AMH structure, one or two maxima of polymerization have been observed.