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

• Published in: Polymer journal Vol. 55; no. 12; pp. 1357 - 1365
• Main Authors: Higaki, Yuji, Toyama, Honoka, Masuda, Takumi, Kobayashi, Shingo, Tanaka, Masaru
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2023; Nature Publishing Group
• Subjects: 140/131; 639/301/923/1028; 639/638/455/960; Addition polymerization; Aqueous solutions; Assembly; Biomaterials; Bioorganic Chemistry; Block copolymers; Chain transfer; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Compartments; Copolymers; Degree of polymerization; Dilution; Hydrophilicity; Molecular chains; Morphology; Original Article; Polymer Sciences; Polymerization; Polymers; Polymethoxyethyl acrylate; Separation; Surfaces and Interfaces; Synthesis; Thin Films; Water chemistry
• ISSN: 0032-3896; 1349-0540
• DOI: 10.1038/s41428-023-00831-3

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. Double-hydrophilic block copolymers composed of a water-soluble poly(carboxybetaine acrylate) and a water-insoluble poly(2-methoxyethyl acrylate) (PCBA2 n - b -PMEA m ) produced particles in dilute aqueous solutions and microphase-separated structures in concentrated aqueous solutions. The microphase-separated structures were associated with the volume fraction and molecular weight-dependent water solubility of the PMEA chain. The morphology of the microphase-separated structure was independent of the polymer concentration, probably because the block copolymer aggregates were isolated as coacervates. The morphology was tolerant to NaCl concentration due to the nonelectrostatic aggregation of PMEA.