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Aqueous dispersion polymerization systems mediated by reversible addition–fragmentation chain transfer (RAFT) process have been less studied in comparison with other heterogeneous polymerization systems due to limited number of monomer/polymer pairs that are suitable for such a condition. We report a novel dispersion polymerization system based on 2-methoxyethyl acrylate (MEA) which is highly water-soluble, but its polymer is not. Using a hydrophilic polymer, poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA), as the macromolecular chain transfer agent (Macro-CTA), both solution and dispersion polymerization of MEA were studied. Chain extension by MEA from PPEGMA was successfully realized in DMF solution polymerization. In dispersion polymerization of MEA in water, PPEGMA was used as both a RAFT mediating species and a steric stabilizer for the formed nanoparticles. The dispersion polymerization of MEA in water was highly efficient using a redox initiator, potassium persulfate/sodium ascorbate, at low temperatures. Simultaneous control of both colloidal stability and RAFT process was realized. Block copolymers with small polydispersity indices were efficiently produced up to complete monomer conversion at solids content up to 32% w/v, in the form of nanoparticles of 40–60 nm diameter.

In situ cross-linking of nano-objects with controllable morphologies in polymerization-induced self-assembly (PISA) has been a challenge because cross-linking lowers chain mobility and hence inhibits morphology transition. Herein, we propose a novel strategy that allows in situ cross-linking of vesicles in PISA in an aqueous dispersion polymerization formulation. This is realized by utilizing an asymmetric cross-linker bearing two vinyl groups of differing reactivities such that cross-linking is delayed to the late stage of polymerization when morphology transition has completed. Cross-linked vesicles with varying degrees (1–5 mol %) of cross-links were prepared, and their resistance to solvent dissolution and surfactant disruption was investigated. It was found that vesicles with ≥2 mol % cross-links were able to retain their structural integrity and colloidal stability when dispersed in DMF or in the presence of 1% of an anionic surfactant sodium dodecyl sulfate.

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