Design of Hydroxy-Functionalized Thermoresponsive Copolymers: Improved Direct Radical Polymerization of Hydroxy-Functional Vinyl Ethers

Abstract

The improved synthesis and aqueous solution properties of hydroxy-functional vinyl ether (OH-VE) copolymers with lower critical solution temperatures (LCST) in water are presented. A series of OH-VE copolymers were directly prepared by free radical polymerization. Effects of water and comonomers on the free radical polymerization using 2-hydroxyethyl vinyl ether (HEVE) were investigated in detail. The free radical polymerization of HEVE at 40–60 wt % in water proceeded with complete monomer conversion. The copolymerizations of HEVE with other vinyl ethers (VEs) or vinyl acetate (VAc) also proceeded smoothly. In each case, the primary key to success in the free radical copolymerization is proper hydrogen bonding between the VE oxygen and hydroxyl group in the pendant or nonacidic water as a solvent. In particular, the copolymerization of OH-VE and VE without a hydroxy group is enabled by a hydrogen-bonded monomer complex. Using the resulting copolymers, we demonstrated the existence of thermoresponsive beh...