Spherical Glycopolymer Architectures using RAFT: From Stars with a ?-Cyclodextrin Core to Thermoresponsive Core–Shell Particles

Abstract

Glycopolymers with a seven-arm star architectures based on a β-cyclodextrin core (β-CD-RAFT) were successfully prepared using reversible addition–fragmentation chain transfer (RAFT) polymerization. A bimodal molecular weight distribution was observed in the early stages of the polymerization. At monomer conversions of N-acryloyl glucose (AGA) above 10% the polymerization proceeded according to a living behaviour and molecular weights of more than 200000 g mol–1 were obtained. However, the resulting star polymers did not undergo well-controlled chain extension with N-isopropyl acrylamide (NIPAAm) and the formation of block structures in each arm was prevented. Alternatively, the arm-first technique was employed. Block copolymers based on AGA and PNIPAAm were self-assembled into micelles at a solution temperature above the lower critical solution temperature. Subsequent core-crosslinking with hexan-1,6-diol diacrylate resulted in unimolecular micelles with thermoresponsive properties. Dynamic light scattering studies, surface tensiometry, and transmission electron microscopy confirmed the formation of core–shell particles.