Precisely Controlled yet Dynamically Exchanged Micelles via the Self-Assembly of Amphiphilic Acrylate Random Copolymers in Water

Abstract

Herein, we investigated the self-assembly of amphiphilic acrylate random copolymers bearing hydrophilic poly(ethylene glycol) chains and hydrophobic dodecyl groups into micelles in water. The random copolymers formed precise yet dynamic micelles in water, dependent on degree of polymerization (DP) and composition. The copolymers shorter than a threshold DP_th exclusively formed multichain micelles and the copolymers longer than the DP_th self-folded into unimer micelles. The molecular weight and size of the multichain micelles were determined by the composition, and the aggregation number was controllable by the DP. Critical micelle concentration of the random copolymers was estimated to be approximately 1 × 10^-3 mg/mL, and almost independent of the DP, aggregation number, monomer sequence, and backbone structures. More uniquely, owing to the flexible backbones, the acrylate random copolymer micelles induced the exchange of polymer chains even at a low temperature such as 10 °C (activation energy: E_a = ~40 kJ/mol) although corresponding methacrylate counterparts with relatively rigid backbones required at least 25 °C for polymer chain exchange.