Hydrosilylation of Allyl Alcohol with [HSiMe2OSiO1.5]8: Octa(3-hydroxypropyldimethylsiloxy)octasilsesquioxane and Its Octamethacrylate Derivative as Potential Precursors to Hybrid Nanocomposites

Octakis(3-hydroxypropyldimethylsiloxy)octasilsesquioxane (OHPS) can be synthesized by direct hydrosilylation of allyl alcohol with octakis(dimethylsiloxy)octasilsesquioxane, (HSiMe2O)Si8O12 (Q8M8H), using platinum divinyltetramethyldisiloxane [Pt(dvs)] as catalyst. Surprisingly, C-hydrosilylation occurs in preference to O-silylation. Hydrosilylation of trimethylsiloxy-2-propene with Q8M8H, followed by desilylation also gives pure OHPS. OHPS reacts with methacryloyl chloride to give octakis(3-methacryloxypropyl-dimethylsiloxy)octasilsesquioxane (OMPS), a thermal and UV/vis curable precursor to organic/inorganic nanocomposites. Direct hydrosilylation of Q8M8H with 2-allyloxyethanol also proceeds primarily via C- rather than O-silylation. In contrast, compounds such as 1,3,5,7-tetramethylcyclotetrasiloxane (D4H), 1,1,3,3-tetramethyldisiloxane (TMDS) or terminal Si−H functionalized poly(dimethylsiloxane) (PDMS-H, MW = 400), give significant amounts of O-silylation along with C-silylation. Initial catalyst con...