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, M_n = 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 polyoligo(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.