Controlled polymerization of hexamethylcyclotrisiloxane was achieved by carrying out the polymerization first at room temperature to about 50% conversion and then at -20 degrees C until complete conversion in order to avoid side reactions. The poly(dimethylsiloxane)s produced show narrow molecular weight distributions (M-w/M-n less than or equal to 1.1). Using this approach, a model linear triblock copolymer PS-6-PDMS-b-PS, as well as 3-miktoarm star co- and terpolymers of the (PDMS)(PS)(2) and (PDMS)(PS)(PI) type, where PS is polystyrene, PI is polyisoprene, and PDMS is poly(dimethylsiloxane), have been prepared.