Thermoresponsive properties of polymer hydrogels induced by copolymerization of hydrophilic and hydrophobic monomers: comprehensive study of monomer sequence and water affinity.

In order to raise the possibility of the practical use of thermoresponsive hydrogels in various fields, it is imperative to achieve on-demand control of responsive behavior especially by using a simple synthetic method with common monomers. To this end, we synthesized various hydrophilic/hydrophobic copolymer hydrogels from common acrylamide derivatives and acrylate monomers via free radical copolymerization, and examined the correlation between the structure and the swelling properties of the obtained gels, specifically from the viewpoint of the monomer sequence in the network chains and the affinity to water molecules. The obtained gels with a hydrophobic acrylamide monomer were shown to exhibit a sharp volume change in water upon heating at suitable monomer compositions.