Functionalized polysilalkylene siloxanes (polycarbosiloxanes) by hydrosilylation—Catalysis and synthesis

Polysilalkylene siloxanes or 'hybrid silicones' are a comparatively new class of polymeric materials combining the chemical properties of silicones and paraffins in a unique way. They can be used as elastomers with remarkable thermal stability and chemical resistance, as wetting agents, surfactants, and hydrophobic coatings. Catalytic hydrosilylation provides a convenient route for the synthesis of these new functional materials. Suitable α,ω-Si–H and α,ω-H2CCH-carriers are combined in step-growth polyaddition reactions. Functionalization and/or activation of silicones by introducing organic, chemically active side groups is of major industrial importance. Silane-functionalized olefins, dienes or polymers have also gained substantial industrial interest. Again, catalytic hydrosilylation is the preferred route to synthesize these compounds, which offer new opportunities for added value materials and applications. In the first part of this review potential catalysts for the hydrosilylation of carbon–carbon double bonds – mainly based on transition metals – are presented and described. The second part deals with the application of such catalyzed hydrosilylation reactions in material science, i.e. in the synthesis of functionalized siloxanes/silicones, of silane-/siloxane-modified organic backbones, and of organosilicon hybrid materials.