Keywords polymeric photoinitiators, ultravioletcuring of acrylic monomers, 4-acryloxyhenzophenone, 4-vinylbenzophenone homopolymers and copolymnersThe synthesis of polymeric photoinitiators having side-chain cyclohexylphenylketone as well as henmphcnonc muietie, at different distances from the backbone is described. Study of the activity uf thc former systems, in the ultraviolet initiated polymerisation of acrylic monomers, indicates that a remarkable increase in thc polymerisation rate is observed when the cyclohexylphenylketone chromophore is attached tci the main chain through an ethereal linkage rather than an ester group. In the case of the latter systems. considerable improvement is observed in the photoinitiating activity with respect to the corresponding low molecular weight model compounds in the polymerisation of acrylic monomers. Moreover, in general the copolymers of benzophenone-containing monomers show higher activity than the corresponding honiopolymcrs. These results are discussed in terms of photoexcitation energy migration along the polymer chain. as well as of intramolecular hydrogen abstraction from both main and side chains. This last occurrence wcms to be the main activation process, as suggested hy a strict correlation between ;ictivity and hydi-ogcn-donating properties of the co-units in the copolymers. Photophysical evidence supporting this point is also reported. Finally, the synthesis of polymeric photoinitiators, containing both benzophenone aird tcrtiary amine groups in the same macromolecule. has been accomplished via copolymerisation of 4-acryloxybenzophenone with 4-(N,N-dimethylamino)styrene. Preliminary data concerning photoinitiating activity of these last copolymers indicate that conformational mobility affects the formation capability of exciplexes and then the activity itself.
