A facile synthesis of branched graft copolymers via combination of RAFT self-condensing vinyl polymerization and aldehyde–aminooxy reaction

Abstract

A facile synthetic route to branched graft copolymers has been developed by combination of self-condensing vinyl polymerization (SCVP), reversible addition–fragmentation chain transfer (RAFT) polymerization and aldehyde–aminooxy reaction. RAFT polymerization of 2-(dimethylamino)ethyl methacrylate (DEM) in the presence of a newly designed aldehyde-containing chain-transfer monomer, 6-(2-formyl-4-vinylphenoxy)hexyl-2-(dodecylthiocarbonothioylthio)-2-methylpropanate (FHDM), led to branched polyDEM (BPDEM) bearing aldehyde functionalities on its branching points. The degree of branching and the average branch length of the resulting BPDEM can be readily tuned by manipulation of the DEM/FHDM feed ratio. The aldehyde groups on the branching points of BPDEM were then reacted with aminooxy-terminated poly(ethylene oxide)s (PEO-ONH₂), affording the structurally well-defined branched graft copolymer BPDEM-g-PEO with a branched polyDEM backbone and PEO grafted chains. The thermo-induced micellization behavior of BPDEM-g-PEO in water was investigated. Opportunities are open for BPDEM-g-PEO to form either multimolecular micelles or unimolecular micelles via simply adjusting the chain length of grafted PEO. Further modification of BPDEM-g-PEO by quaternization resulted in branched cationic polyelectrolytes which are capable of capturing negatively charged guest molecules via electrostatic complexation to form in situ self-assembled nanoparticles with simultaneous encapsulation of the guests.