Exhaustive and partial alkoxylation of polymethylhydrosiloxane by copper-catalyzed dehydrocoupling with alcohols: Synthesis, crosslinking behavior, and thermal properties of the products



Polymethylhydrosiloxane (PMHS) reacts with aliphatic and aromatic alcohols at room temperature in the presence of [CuH(PPh3)]6 complex catalyst to give poly[(methyl) (alkoxy)siloxane]s in high yields. Reactivity of alcohols decreases in the order of p-methoxyphenol > p-cresol > phenol > benzyl alcohol > allyl alcohol > ethanol > isopropanol > tert-butyl alcohol. Partially p-cresylated polymers, which still retain unreacted Si[BOND]H bonds, react further with ethylene glycol or water to form cross-linked polymers, which, depending on the extent of cross linking, gelate during the cross-linking process. Propargyl alcohol reacts with PMHS very rapidly to give exhaustively and partially propargyloxylated PMHS. Resulting polymers, upon heating, undergo crosslinking. Partially propargyloxylated polymers display high thermal stability [Td5 (temperature of 5% weight loss) > 500 °C] as compared with starting PMHS (243 °C) and exhaustively propargyloxylated one (414 °C). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011