Synthesis of ABC 3-miktoarm star terpolymers from a trifunctional initiator by combining ring-opening polymerization, atom transfer radical polymerization, and nitroxide-mediated radical polymerization

We report a new method to synthesize ABC 3-miktoarm star terpolymers by combining three different controlled/"living" polymerization techniques: ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP), and nitroxide-mediated radical polymerization (NMRP). A trifunctional initiator bearing a hydroxy group, an ATRP initiator, and a NMRP initiator was designed and synthesized. The structure was confirmed by H-1 NMR, C-13 NMR, and mass spectroscopy. ABC star terpolymers were then prepared from the trifunctional initiator by sequential ROP of epsilon-caprolactone, ATRP of methyl methacrylate, and NMRP of styrene. GPC and kinetic analysis indicated that the polymerizations were controlled. The 3-miktoarm star structure was further confirmed by cleavage of a star terpolymer.