Synthesis of AB2 3- and AB4 5-miktoarm star copolymers initiated from dendritic tri- and penta- functional initiators by combination of ring-opening polymerization of ε-caprolactone and nitroxide-mediated radical polymerization of styrene

Well-defined AB(2) 3- and AB(4) 5-miktoarm star copolymers were prepared by combination of ring-opening polymerization (ROP) and nitroxide-mediated radical polymerization (NMRP) using dendritic tri- and penta-functional initiators. Initially, two kinds of dendritic initiators having one benzylic OH and two or four TEMPO-based alkoxyamine moieties were prepared. Using them, ROP of epsilon-caprolactone was carried out at room temperature to give poly(g-caprolactone)s carrying two or four alkoxyamine moieties. NMRP of styrene from the poly(E-caprolactone)s was carried out at 120degreesC to give AB, 3- and AB4 5-miktoarm star copolymers, which were analyzed by H-1 NMR and SEC. Tie (M) over bar S-n increased linearly with conversion and the (M) over bar (w)/(M) over bar (n)s were in the range 1.10-1.37, showing that well-defined AB(2)3- and AB(4)5-miktoarm star copolymers were formed.