Thermoresponsive Properties of Copolymers in Aqueous Solvents Induced by Hydrophilic/Hydrophobic Sequence Control

Abstract

This review summarizes the solution and gel properties of amphiphilic copolymers consisting of hydrophilic and hydrophobic monomers in aqueous media. A random copolymer prepared from an appropriate combination of monomers exhibits thermoresponsive behavior in water, i.e. soluble–insoluble transition in solution and swelling–shrinking in the gel state, due to fine balance of hydration and hydrophobic interaction, as similarly observed in the well-known thermoresponsive polymer poly（N-isopropylacrylamide）. Since the solution properties of polymers are greatly affected by the sequence of two kinds of monomers along the polymer chains, an alternating polymer would be an excellent model for deep understanding the behavior of polymers in a solution. Conventional and recent synthetic strategies for alternating polymers are briefly introduced, and the intriguing phenomena, including self-assembly behavior, based on amphiphilic alternating structures are outlined. In particular, we have recently discovered an alternating copolymer composed of N-ethylmaleimide and 2-hydroxyethyl vinyl ether exhibits cosolvency in a water/ethanol binary solvent system.