Synthesis and properties of photoreactive polysiloxanes containing pendant functional groups

Functional polysiloxanes containing photo-reactive pendant groups were prepared by multi-step modification of silicone copolymers containing methylhydrosiloxanes units. A first method based on the platinum Catalyzed hydrosilylation of vinylsilyl terminated photoreactive esters allowed to prepare liquid silicone polymers containing photo-dimerizable esters. Another method based of the esterification of pendant epoxy groups previously grafted on the silicone main chain was found as a general and very powerful alternative route to prepare photo-reactive polysiloxanes. The method has been applied to synthesize polysiloxanes containing various functional side-groups such as dimerizable esters, aromatic carbonyl compounds or dyes which possess properties of photochemical interest. The reactivity, the ability to be photosensitized as well as some practical properties of different photo-crosslinkable polysiloxanes modified either by cinnamic, furacrylic or a cyano p styrylacrylic ester groups were examined. A kinetic investigation of the reactivity of the polysiloxane-bound dimerizable chromophores allows to point out the effect of the silicone matrix in comparison with more classical hydrocarbon pho topolymer 8.