Synthesis and characterization of hyperbranched amphiphilic block copolymers prepared via self-condensing RAFT polymerization

Abstract

Four families of hyperbranched amphiphilic block copolymers of styrene (Sty, less polar monomer) and 2-vinylpyridine (2VPy, one of the two more polar monomers) or 4-vinylpyridine (4VPy, the other polar monomer) were prepared via self-condensing vinyl reversible addition-fragmentation chain transfer polymerization (SCVP-RAFT). Two families contained 4VPy as the more polar monomer, one of which possessing a Sty-b-4VPy architecture, and the other possessing the reverse block architecture. The other two families bore 2VPy as the more polar monomer and had either a 2VPy-b-Sty or a Sty-b-2VPy architecture. Characterization of the hyperbranched block copolymers in terms of their molecular weights and compositions indicated better control when the VPy monomers were polymerized first. Control over the molecular weights of the hyperbranched copolymers was also confirmed with the aminolysis of the dithioester moiety at the branching points to produce linear polymers with number-average molecular weights slightly greater than the theoretically expected ones, due to recombination of the resulting thiol-terminated linear polymers. The amphiphilicity of the hyperbranched copolymers led to their self-assembly in selective solvents, which was probed using atomic force microscopy and dynamic light scattering, which indicated the formation of large spherical micelles of uniform diameter. © 2015 Wiley Periodicals, Inc.