Synthesis of porous poly[oligo(ethylene glycol) methyl ether methacrylate] gels that exhibit thermosensitivity in highly concentrated aqueous NaCl solution

The polymerization of 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) in 20 wt% aqueous ethanol solution and oligo(ethylene glycol) methyl ether methacrylate (OEGMA300, Mn = 300 g mol−1) in water was carried out in the presence of a crosslinker. Polymerization at temperatures above the lower critical solution temperature (LCST) yielded the corresponding porous poly[oligo(ethylene glycol) methyl ether methacrylate] gels by polymerization-induced phase separation. The resulting porous gels showed rapid swelling-deswelling in water. The temperature dependency of the equilibrium swelling ratio of the gels was investigated in several concentrated aqueous NaCl solutions. At 20 °C, the equilibrium swelling ratios of the POEGMA300 gel obtained from OEGMA300 were largely unaffected by NaCl concentration; however, above 30 °C, they decreased with increasing NaCl concentration. Therefore, the POEGMA300 gel showed sharp and high thermosensitivity in highly concentrated aqueous NaCl solutions. Similar swelling behaviors were observed for PMEO2MA gel, which was prepared from MEO2MA.