Mechanical properties of pH-responsive poly(2-hydroxyethyl methacrylate/methacrylic acid) microgels prepared by inverse microemulsion polymerization

The structure and mechanical properties of monodisperse pH-responsive poly(2-hydroxyethyl methacrylate/methacrylic acid) (poly(HEMA/MAA)) microgels prepared by inverse microemulsion polymerization were systematically investigated. To facilitate the polymerization, the inverse microemulsion systems were first optimized by generating relevant pseudo-three-component phase diagrams. The reactivity ratios of HEMA (r1 = 1.001 ± 0.064) and MAA (r2 = 0.318 ± 0.035) determined by titration method suggested that PHEMA segments preferred to be localized in the core of the synthesized poly(HEMA/MAA)) microgels. The mechanical property studies of the microscopic poly(HEMA/MAA)) microgels from oscillation rheometry revealed that microgel composition, concentration and pH could significantly alter the elastic modulus (G′), and a maximum averaged elastic modulus (Gave′) value of about 8.2 × 103 Pa was obtained.