Modification of block copolymer vesicles: what will happen when AB diblock copolymer is block-extended to an ABC triblock terpolymer?

Well-defined vesicles of poly(ethylene glycol)-block-polystyrene (PEG-b-PS) were prepared through the macro-RAFT agent mediated dispersion polymerization, and the modification of the PEG-b-PS vesicles by the extension of a third solvophilic poly(4-vinylpyridine) block through seeded RAFT polymerization was investigated. It was found, during the seeded RAFT polymerization, that the PEG-b-PS diblock copolymer was extended to the poly(ethylene glycol)-block-polystyrene-block-poly(4-vinylpyridine) (PEG-b-PS-b-P4VP) triblock terpolymer, and the PEG-b-PS vesicles were converted into the membrane-compartmentalized PEG-b-PS-b-P4VP vesicles (MCVs). In the MCVs, the poly(4-vinylpyridine) chains were found to be uniformly distributed in the inner side of the membrane, whereas on the outer side of the membrane several poly(4-vinylpyridine) chains were converged together and were segregated by the neighbouring poly(ethylene glycol) chains. The proposed seeded RAFT polymerization may be a promising method of vesicle modification, and the MCVs with segregated membrane structure are deemed to be a new morphology of the block copolymer nano-assemblies.