Thermoresponsive ultrafiltration membrane from polymerization of lyotropic liquid crystals

In this work, we present the fabrication of a two-step thermoresponsive ultrafiltration (UF) membrane through polymerization of a lyotropic liquid crystal (LLC). A lamellar LLC is produced from a mixture of poly[(ethylene oxide)₁₀₀-block-(propylene oxide)₆₅-block-(ethylene oxide)₁₀₀], water (containing ammonium persulfate as the initiator), and polymerizable oil (n-butyl acrylate/ethylene glycol dimethacrylate). Differential scanning calorimetry is employed to evaluate the thermoresponsive behavior of the polymerized LLC (polyLLC). Two-step thermoresponsiveness (~35 °C and ~50 °C) of the polyLLC is observed due to the lower critical solution temperature (LCST) of block copolymer and melting of the crystalline structure of the polyethylene oxide (PEO) block. The obtained mesophase is then cast on a nonwoven polyester support sheet followed by thermal polymerization to form a supported UF membrane. The hydration capacity, water flux, water flux recovery after fouling, and molecular weight cut-off (MWCO) of the obtained membrane are evaluated at different temperatures to examine its thermoresponsiveness. The experimental results reveal that the UF membrane has a reversible thermoresponsive behavior at the LCST and PEO melting of polyLLC. Additionally, the MWCO of the membrane can be altered with temperature due to the pore size change with temperature stimulus.