Thermosensitive poly (N-isopropylacrylamide) hydrophobic associated hydrogels: optical, swelling/deswelling, and mechanical properties

Thermosensitive hydrophobic associated hydrogels (NI-HA gels) were prepared by free radical micellar copolymerization in aqueous solution of N-isopropylacrylamide, a small amount of hydrophobic monomer octylphenol polyoxyethylene (4) acrylate (OP4~AC), and nonionic surfactants. The mechanical properties, swelling/deswelling behaviors, and optical transmittances of NI-HA gels were studied. As OP4~AC content varied, both mechanical properties and swelling behaviors of gels changed greatly. The temperature-induced changes in optical transmittance and deswelling tests showed that NI-HA gels had rapid temperature responsive rate and clear volume phase transitions at around 34 °C, and these properties had almost no concern with OP4~AC content. Furthermore, NI-HA gels also possessed extremely sensitive swelling/deswelling switch behaviors and well swelling stabilities.