Self-Assembly of Amphiphilic Alternating Copolymers by Chain Folding in Water: From Uniform Composition and Sequence to Monodisperse Micelles

Self-assembly systems of amphiphilic copolymers in water have been developed to create nano-objects with target structures, properties, and functions, whereas reducing the structural distribution toward uniform self-assemblies is still a challenging issue. Herein, we report precision self-assembly of amphiphilic alternating copolymers into monodisperse micelles via chain folding in water. For this purpose, we synthesized an alternating copolymer bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dodecyl groups via the radical copolymerization of PEG methyl ether acrylate (PEGA) in the presence of an excess amount of dodecyl vinyl ether (DVE). The PEGA/DVE alternating copolymers induced self-folding and intermolecular self-assembly into unimer and multichain micelles, dependent on the degree of polymerization (DP): The aggregation number of the micelles can be controlled by tuning DP, and the copolymers shorter than the threshold DP of 200 exclusively formed multichain micelles. Owing to the uniform composition and monomer sequence, the PEGA/DVE alternating copolymer formed a monodisperse multichain micelle; the apparent size distribution of the alternating copolymer micelle was narrower than that of a corresponding acrylate-type random copolymer. Furthermore, the alternating copolymer micelle sharply and reversibly showed lower critical solution temperature-type thermoresponsive solubility in water.