Controlled synthesis of siloxane polymers and siloxane-siloxane block copolymers with 3-chloropropyl groups pendant to the siloxane chain

Linear polysiloxanes bearing 3-chloropropyl groups pendant to the polymer c hain and containing a vinyl functional group at one chain end were synthesi zed by anionic ring polymerizations of 2,4,6-tri(3-chloropropyl)-2,4,6-trim ethylcyclotrisiloxane, 1, and 2-(3-chloropropyl)-2,4,4,6,6-pentamethylcyclo trisiloxane, 2, initiated with butyl lithium silanolate in tetrahydrofuran. The polymerizations led to high yields of polymers with narrow molecular w eight distributions. The precise functionalizations of the polymers were pe rformed by a termination method quenching the polymerization by dimethyl-vi nylchlorosilane. Diblock copolymers AB of narrow molecular weight distribut ionand a high topological purity were obtained by the sequential anionic co polymerization of hexamethylcyclotrisiloxane D-3,with monomers 1 and 2.