Photoinitiation of Addition Polymerization

Photoinitiation of Addition Polymerization.—Much of the research reported in this section has arisen from commercial and environmental needs for surface coatings which do not rely on polymerization in solvent media. One approach to this problem has been to initiate the addition polymerization of monomer/ oligomer/pigment formulations with u.v. light and suitable photoinitiators. The initiators most commonly used are benzophenone, Michler s ketone (1), and benzoin ethers, but the search for other efficient photoinitiators continues. 

Many applications of metal salts as photoinitiators have been described. These include (i) vinyl monomer polymerization using iron(m) salt-saccharide systems 1 (ii) mixtures of tetraphenylporphineiron(m), amine, and CC14 2 

In the case of isobutene-VCl4 mixtures, a spectroscopic study revealed that the initiator was a coloured complex of VC14 and the monomer, photoinitiation accounting for all of the polymerization at 253 K, but thermal initiation becoming 

The results also showed that the isomerization of MeO to CH2OH may be catalysed by a vanadium species, and that chelates of the type considered can be incorporated into polymers by two methods to give photosensitive products which undergo grafting and cross-linking reactions on irradiation. 

MMA has also been polymerized by photoinitiation with iodine,8 iodine-monoethanolamine mixtures, quinoline-bromine charge-transfer complexes,10 and quinoxaline derivatives.11 The initiation with iodine was not attributed to simple dissociation of molecular iodine, but rather to absorption by an iodine-monomer (M) complex [reaction (3)]. A 1 1 complex between Ia and mono- 

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