Synthesis of an organosilicon hyperbranched oligomer containing alkenyl and silyl hydride groups

A new organosilicon hyperbranched oligomer has been prepared that contains both double bonds and silyl hydride groups. The monomer is prepared via the hydrosilylation of propargyl chloride with methyldichlorosilane in the pre sence of a platinum catalyst. The product is a mixture resulting from both alpha- and beta-addition. Treatment of the monomer mixture with magnesium r esults in the formation of a hyperbranched oligomer, which is then treated with LiAlH4. Control of monomer addition speed to the magnesium is critical in order to keep head-head coupling low. The resulting oligomer is air- an d water-stable, and has an average degree of polymerization of 8. This mate rial gives a char yield of 24% but after crosslinking with platinum catalys t, the char yield increases to 69%. (C) 1999 John Wiley & Sons, Inc.