Synthesis of functional telechelic polydimethylsiloxanes by ion-exchangerscatalysis

Telechelic siloxane oligomers with vinyl-, aminopropyl- methylmethacryloxy- and carboxypropyl- groups were obtained by ion-exchanger catalysed equilib ration reactions between octamethylcyclotetrasiloxane and proper 1,3-difunc tional disiloxanes. Depending on the nature of the functional group (i.e. a cid or basic) either cation- or anion-exchangers were employed, in order to prevent catalyst deactivation and side reactions. The conditions in which oligomers with desired molecular weights can be obt ained have been established. (C) 1999 Elsevier Science Ltd. All rights rese rved.