Synthesis and properties of a dual responsive hydrogel by inverse microemulsion polymerization

A novel dual responsive hydrogel was synthesized by inverse microemulsion polymerization, using itaconic acid as pH-responsive monomer and N- isopropylacrylamide as thermo-responsive monomer. pH- and temperature-sensitivity and dynamic viscoelasticity behaviour of the dual responsive hydrogels were investigated. Dual responsive hydrogels showed remarkable pH- and temperature-sensitivity and enhanced viscoelastic behaviour under high stress. Temperature-induced shrinkage range of the dual responsive hydrogels was higher and broader than that of the conventional poly(N-isopropylacrylamide) hydrogel. FTIR revealed the structure of dual responsive hydrogels. The as-synthesized regular and sphere-like hydrogel particles had the average particle size of 49 nm in the range of 30–78 nm.