Photoinitiation mechanisms

Strohmeier and Hartmann [14] first reported in 1964 the photoinitiation of polymerization of ethyl acrylate by several transition metal carbonyls in the presence of CCI4. Vinyl chloride has also been polymerized in a similar manner [15,16] No detailed photoinitiation mechanisms were discussed, but it seems most likely that photoinitiation proceeds by the route shown in reaction Scheme (9). 

The chemistry of the oxidative and nonoxidative photodegradation of poly(vinyl chloride) is reviewed with emphasis on work that has been published since the early 1970 s. Topics covered include the nature of the photoinitiating species, the photoinitiation mechanism, and the structural consequences and reaction mechanism of the overall photodegradation process. Also included is a summary of recent studies on the determination of structural defects in poly(vinyl chloride) by carbon-13 NMR. 

Chang, C. H., Mar, A., Tiefenthaler, A., and Wostratzky, D. "Photoinitiators Mechanisms and Applications", a publication form Ciba-Geigy Corporation, Hawthorne, New York. 

Novel photoinitiated mechanisms of polymerization have also been developed to pattern cellular behavior within bulk hydrogel constmcts. For example, a sequential cross-linking technique was used to pattern MSG spreading within adhesive and enzymatically degradable HA... 

Kutal et reviewed the chemistry of several iron (II) metallocenes that are effective photoinitiators for ionic polymerization reactions. Photoexcitation of ferrocene and 1,1-dibenzoyl -ferrocenes in solutions of ethyl-a-cyanoacrylate produces anionic species that initiate the polymerization of electrophilic monomers. Irradiation of CsHs-Fe (t] - arene) in epoxide containing media generates several cationic species capable of initiating ringopening polymerizations. It was concluded that iron(II) metallocenes exhibit a diversity of photoinitiation mechanisms. 

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