One-pot preparation of BAB triblock copolymer nano-objects through bifunctional macromolecular RAFT agent mediated dispersion polymerization

One-pot preparation of the BAB triblock copolymer nano-objects of polystyrene-block-poly(4-vinylpyridine)-block-polystyrene (PS-b-P4VP-b-PS) containing a central solvophilic A block and two outer solvophobic B blocks through dispersion RAFT polymerization is proposed. Ascribed to the bifunctional macro-RAFT agent of bis(trithiocarbonate)-terminated poly(4-vinylpyridine) (TTC-P4VP-TTC), which contains two functional RAFT moieties at each terminal of the polymer backbone, the bifunctional TTC-P4VP-TTC macro-RAFT agent mediated dispersion polymerization affords the in situ synthesis of the PS-b-P4VP-b-PS triblock copolymer nano-objects. The parameters affecting the morphology of the PS-b-P4VP-b-PS triblock copolymer nano-objects are investigated, and it is found that the morphology of the PS-b-P4VP-b-PS nano-objects undergoes a transition from nanospheres, to worms, to vesicles and finally to lacunal nanospheres with the extension of the PS block during the dispersion RAFT polymerization. The bifunctional macro-RAFT agent mediated dispersion polymerization is demonstrated to be a valid method to prepare BAB triblock copolymer nano-objects with interesting morphology.