Photolysis of polysilanes

Silicon centered radicals can be generated by transfer to silanes and by photolysis of polysilanes. Rate constants for addition to monomer are several orders of magnitude higher than similar carbon centered radicals.453,43 The radicals have nucleophilic character. 

Photoinitiation. Since photolysis of polysilanes generates silyl radicals, which can add to carbon—carbon double bonds, these polymers have been used for the free-radical polymerization of unsaturated oiganic monomers (135,136). Though about one-tenth as efficient as other oiganic photoinitiators, polysilanes are nevertheless quite insensitive to oxygen effects, which somewhat compensates for their lower efficiency. 

Photolysis of polysilanes produces silyl radicals, which can be used to induce free-radical reactions. Because the silyl radicals can add to carbon-carbon double bonds and begin the formation of polymer chains, polysilanes can be used as radical photoinitiators. In early studies, (PhSiMe) and its copolymers (PhQIUSiMe), and (cyclo-HexSiMe) were shown to photoinitiate the polymerization of styrene and several acrylate... 

Similar to pyridinium salts, iodonium salts can be reduced by silyl radicals generated by photolysis of polysilanes. However, due to the tail absorption bands of iodonium salts at about 300 nm, polysilanes with relatively longer... 

Z ) Some other methods of silylene generation are by the photolysis of polysilanes. 

Polysilanes are connected with carbon polymers to form A-B and A-B-A type block pol5uners. Reaction of Li-terminated polyst5Tene with cyclotetrasilanes (73) or halogen-terminated polysilanes (74), photolysis of polysilanes in carbon monomers (methacrylic monomers) (75), or reaction of halogen-ended polysilanes with poly(ethylene glycol) affords A-B and/or A-B-A type Block Copolymers (qv) (76) (Fig. 8). Comb-like Graft Copolymers (qv) have also been prepared by reaction of triflate-substituted poly(methylphenylsilane) with THF, 2-methyl-2-oxazoline, or isobutyl vinyl ether (77). 

Dimethylsilylene Me Si has been generated by photolysis of polysilanes such as (Me Si),. 

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