Photoinitiators macro

Photopolymerization using polysilanes can also be carried out to yield block copolymers containing runs of silicon atoms, for instance polysilane-methyl methacrylate. The resulting copolymer can then be used as a macro-photoinitiator for further free-radical polymerizations.144145... 

In spite of the numerous studies reported on photooxidation of polyolefins, the detailed mechanism of the complete process remains unresolved. The relative contribution by species involved in photoinitiation, the origins of the oxidative scission reaction, and the role played by morphology in the case of photoreactions in solid state are not completely understood. Primary initiator species in polyethylenes [123] and polypropylenes [124] are believed to be mainly ketones and hydroperoxides. During early oxidation hydroperoxides are the dominant initiator, particularly in polypropylene, and can be photolyzed by wavelengths in solar radiation [125]. Macro-oxy radicals from photolysis of polyethylene hydroperoxides undergo rapid conversion to nonradical oxy products as evidenced by ESR studies [126]. Some of the products formed are ketones susceptible to Norrish I and II reactions leading to chain scission [127,128]. Norrish II reactions predominate under ambient conditions [129]. Concurrent with chain scission, crosslinking, for instance via alkoxy macroradical combination [126], can take place with consequent gel formation [130,131]. 

Viklund, C. Ponten, E. Glad, B. Irgum, K. Horstedt, P. Svec, F. Molded Macro-porous poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate) materials with fine controlled porous properties preparation of monoliths using photoinitiated polymerization. Chem. Mater. 1997, 9, 463-471. 

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