Swelling behavior of thermosensitive nanocomposite hydrogels composed of oligo(ethylene glycol) methacrylates and clay

Novel thermosensitive nanocomposite (NC) hydrogels have been synthesized by copolymerization of 2-(2-methoxyethoxy) ethyl methacrylate (MEO(2)MA), oligo(ethylene glycol) methacrylate (OEGMA), and using inorganic clay as cross-linker via in-situ free radical polymerization. The structure and morphology of clay/P(MEO(2)MA-co-OEGMA) NC hydrogels, were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM), and the results indicated that the inorganic clay was uniformly dispersed in the NC hydrogels and obviously affected the network structure. Furthermore, physical properties such as equilibrium swelling/deswelling ratio, water retention, reversible thermosensitivity, and temperature dependence behaviors of NC hydrogels with different chemical compositions (molar ratio of comonomer, clay, and mass fraction of polymer) were investigated carefully. Moreover, the deswelling kinetics at specific temperature was studied, and the deswelling rates were well described with a first-order kinetics equation. The results indicated that the obtained NC hydrogels showed a controllable equilibrium swelling/deswelling behavior and possessed remarkable thermosensitivity. In addition, when the molar ratio of MEO(2)MA and OEGMA was 80 mol%: 20 mol%, the equilibrium swelling ratio of NC hydrogels with 5 wt% clay reached 1640%, which is four times higher than that of N,N'-methylenebisacrylamide cross-linked hydrogels (410%). Consequently, this novel clay/P(MEO(2)MA-co-OEGMA) NC hydrogel with interesting thermosensitive properties would be promising for potential applications, such as stimuli-responsive valve, drug delivery system, artificial muscle, and biosensor. (C) 2015 Elsevier Ltd. All rights reserved.