Syntheses of AB2 3- and AB4 5-miktoarm star copolymers by combination of the anionic ring-opening polymerization of hexamethylcyclotrisiloxane and nitroxide-mediated radical polymerization of styrene

AB2 3- and AB4 5-miktoarm star copolymers were prepared by combination of the anionic ring-opening polymerization (AROP) of hexamethylcyclotrisiloxane (D3) and the TEMPO-mediated radical polymerization of styrene (St). Initially, two kinds of dendritic multifunctional initiators were prepared. One has a 4-bromobutoxy group and two TEMPO-based alkoxyamines and the other has a 4-bromobutoxy group and four TEMPO-based alkoxyamines. Treatment of the multifunctional initiators with tert-butyllithium gave the corresponding lithiobutoxy derivatives, and AROP of D3 by the lithiobutoxy derivatives gave poly(D3) with Mw/Mn of 1.07-1.12. Nitroxide-mediated radical polymerization of St by the poly(D3)s at 120 °C gave AB2 3- and AB4 5-miktoarm star copolymers with Mw/Mn of 1.15-1.28. Their structures were analyzed by means of 1H NMR and SEC measurements.