WACKER IM 11 is a polydimethylsiloxane having organofunctional groups in ?,?-position. By functionalizing the polydimethylsiloxanes on the ends of the chain defined products are obtained having a functionality of 2. The functional groups are bonded to the polydimethyl-siloxane by chemically inert alkylene spacergroups, which are stable to hydrolysis. Due to their ?,?-functionalization each polymer chain has exactly two organofunctional groups.