Copper-coordination induced fabrication of stimuli-responsive polymersomes from amphiphilic block copolymer containing pendant thioethers†
Abstract
In this work, we synthesized oxidation-responsive amphiphilic block copolymers PEG45-b-P(MET/PBC)n bearing pendant phenylboronic ester carbamate (PBC) and thioether moieties in the hydrophobic block by RAFT polymerization and post-polymerization modification. As the hydrophobic block length increased, the polymeric self-assemblies underwent a morphological transition from spherical micelles to worm-like micelles to bilayered polymersomes. Triggered by H2O2, the polymersomes disintegrated because of the oxidation of thioether to sulfoxides and the decomposition of PBC moieties. Taking advantage of the thioether–copper coordination capability, the hybrid polymersomes with Cu2+-cross-linked membrane were fabricated via the co-assembly of the block copolymer with Cu2+ ions, driven by the coordination interactions between the hydrophobic block and Cu2+ ions. The metal–ligand interaction endows the hybrid polymersomes with a responsive property to the competitive ligand. In the presence of glutathione (GSH) (or sodium ascorbate) and H2O2, Cu+ ions were in situ produced via the reduction of the entrapped Cu2+ ions and subsequently initiated a Fenton-like reaction to generate hydroxyl radicals. The catalytic activity of the hybrid polymersomes-mediated Fenton-like reaction was evaluated by the oxidation of terephthalic acid and the degradation of methylene blue, respectively. In the presence of H2O2 and GSH, the hybrid polymersomes underwent a shape change and transformed into a mixture of spherical micelles and worm-like micelles.