Sugar-coated amphiphilic block copolymer micelles from living radical polymerization: Recognition by immobilized lectins

Block copolymers poly[((ethylene glycol)methyl ether methaerylate)-b-(benzyl methacrylate)] containing protected sugar groups were synthesized by transition-metal-mediated living radical polymerization. Sugar-derived initiators were prepared by esterification of the hydroxyl group of isopropylidene-protected galactose and glucose with 2-bromoisobutyryl bromide. Both protected galactose and glucose-derived initiators were respectively used to initiate the hydrophilic monomer (PEGMA) and the hydrophobic monomer (BzMA) in both one-pot and two-step polymerizations. In both cases the polymerization occurred with good first-order kinetics, producing AB blocks with molecular weights close to that targeted and with low polydispersity (1.1-1.2). Following removal of the isopropylidene protective groups via acidolysis with 50% trifluoroacetic acid (TFA) at ambient temperature, block copolymer micelles were obtained by a dialysis solvent exchange process. The size and polydispersity of the polymer micelle were estimated by dynamic light scattering, and the Z-averaged hydrodynamic diameters were found to be between 35 and 41 nm with a unimodal size distribution. Furthermore, the binding ability of a galactose bearing copolymer micelles was confirmed by recognition with an HPLC column packed with immobilized RCA-1 lectin.