Precision Synthesis of Imine-Functionalized Reversible Microgel Star Polymers via Dynamic Covalent Cross-Linking of Hydrogen-Bonding Block Copolymer Micelles

• Published in: Macromolecules Vol. 50; no. 2; pp. 587 - 596
• Main Authors: Azuma, Yusuke, Terashima, Takaya, Sawamoto, Mitsuo
• Format: Journal Article
• Language: English
• Published: American Chemical Society 24-01-2017
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.6b02403

Imine-functionalized reversible microgel star polymers were synthesized by dynamic covalent cross-linking of hydrogen-bonding block copolymer micelles in organic media. This approach allows the precision and wide range control of molecular weight (M w = 100–10 000 K; M w/M n = ∼1.1) of star polymers via preforming micelles of block copolymers. For this, a urea and aniline-functionalized methacrylate (ApUMA) was newly designed as a key monomer. The block copolymer of methyl methacrylate (MMA) and ApUMA, prepared by ruthenium-catalyzed living radical polymerization, efficiently self-assembled into micelles via hydrogen-bonding interaction of the urea pendants in dichloromethane and dichloromethane/N,N-dimethylformamide mixture. The subsequent treatment with terephthalaldehyde gave imine-cross-linked star polymers with quite narrow distribution in high yield. The molecular weight of the star polymers was successfully controlled by tuning solvents, concentration, and the block copolymer structure (PMMA arm and ApUMA segment length). Imine-functionalized star polymers have dynamic covalent and multifunctional microgels to afford pH-responsive or transimination-mediated structure transformation, pH-sensing, and postfunctionalization.