Development of thermosensitive copolymers of poly(2-methoxyethyl acrylate-co-poly(ethylene glycol) methyl ether acrylate) and their nanogels synthesized by RAFT dispersion polymerization in water

Thermosensitive polymeric materials based on copolymers of oligo(ethylene glycol) methacrylates are attracting significant attention in various materials sectors. The preparation of their thermosensitive microgels/nanogels via the aqueous dispersion polymerization process is, however, limited by low monomer loading and thus low solid content of the final colloids. Moreover, the preparation of nanogels by reversible addition-fragmentation chain transfer (RAFT) mediated dispersion polymerization has been further hampered by the poor RAFT control of the polymerization process. In this article, we report the development of thermosensitive copolymers based on poly(2-methoxyethyl acrylate-co-poly(ethylene glycol) methyl ether acrylate) (P(MEA-co-PEGA)) and their use for nanogel synthesis by RAFT dispersion polymerization in water. The thermosensitive copolymers exhibited sharp thermal transitions upon increasing thee temperature above their lower critical solution temperature. The use of MEA as the majority comonomer and poly(N,N'-dimethylacrylamide) as the RAFT agent and stabilizer for the synthesis of nanogels allowed monomer loadings of up to 20%, which significantly improved the solid content of the dispersion polymerization system. Moreover, the dispersion copolymerization of MEA with PEGA was under excellent RAFT control up to complete monomer conversion. The synthesized nanogels showed an unprecedented linear relationship between nanogel size and temperature, suggesting expanded applications of such responsive polymeric materials.