Shape-shifting thermoresponsive diblock copolymer nano-objects via polymerization-induced self-assembly

Abstract: Polymerization-induced self-assembly (PISA) is a powerful and versatile technique for the rational synthesis of concentrated dispersions of block copolymer nano-objects of controllable size, shape and surface chemistry. PISA can be conducted in aqueous media using reversible addition-fragmentation chain transfer (RAFT) polymerization. In this context, RAFT aqueous dispersion polymerization formulations are rather scarce because there are relatively few water-miscible vinyl monomers that form water-insoluble polymers. However, such syntheses afford various examples of stimulus-responsive nano-objects that undergo morphological transitions on varying the solution pH or temperature. For example, herein we report new examples of amphiphilic thermoresponsive diblock copolymers of fixed composition that can form spheres, worms or vesicles simply by varying the solution temperature. Such unprecedented self-assembly behavior is characterised by TEM, DLS, rheology and SAXS and is shown to be the result of subtle variation in the degree of (partial) solvation of the weakly hydrophobic block.

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