Microphase separation of double-hydrophilic poly(carboxybetaine acrylate)-poly(2-methoxyethyl acrylate) block copolymers in water

The microphase separation of double-hydrophilic block copolymers in water is of interest when these copolymers are utilized as molecular assemblies with mesoscale aqueous compartments. Diblock copolymers composed of a water-soluble zwitterionic polymer, poly(carboxybetaine acrylate) (PCBA2), and a hydrophilic water-insoluble nonionic polymer, poly(2-methoxyethyl acrylate) (PMEA), (PCBA2 n - b -PMEA m ) were synthesized, and their assembly characteristics were investigated in aqueous solutions. Well-defined PCBA2 n - b -PMEA m block copolymers were synthesized by the reversible addition–fragmentation chain transfer polymerization of a carboxybetaine acrylate modified with a tert -butyl group and 2-methoxyethyl acrylate followed by tert -butyl group cleavage. PCBA2 n - b -PMEA m produced particles in dilute aqueous solutions and microphase-separated structures in concentrated aqueous solutions. The hydrodynamic radius of the particles and the microphase-separated structure were associated with the block copolymer composition and degree of polymerization of the PMEA chain. The molecular assembly behavior was tolerant to NaCl concentration, providing molecular design guidelines for the use of double-hydrophilic microphase-separated compartments in physiological environments.