In situ synthesis of a self-assembled AB/B blend of poly(ethylene glycol)-b-polystyrene/polystyrene by dispersion RAFT polymerization

A diblock-copolymer/homopolymer self-assembled blend of poly( ethylene glycol)-block-polystyrene/ polystyrene (PEG-b-PS/PS) was synthesized through dispersion RAFT polymerization. In this dispersion RAFT polymerization reaction, a macro-RAFT agent and a small RAFT agent containing the same RAFT moiety were simultaneously used. By tuning the molar ratio of the macro-RAFT agent and the small RAFT agent fed into the dispersion RAFT polymerization mixture, PEG-b-PS/PS self-assembled blends with different morphologies could be prepared. It is found that the PEG-b-PS/PS self-assembled blend synthesized by dispersion RAFT polymerization is very different from the blend prepared via micellization of a pre-synthesized PEG-b-PS/PS mixture, and its morphology changes from vesicles, to compartmentalized vesicles and finally to porous nanospheres with a decreasing ratio of PEG-b-PS/PS in the blends. It is believed that the present dispersion RAFT polymerization technique, which simultaneously uses a macro-RAFT agent and a small RAFT agent, is a valid method to synthesize self-assembled block copolymer blends.