Temperature-responsive poly(tetrafluoroethylene) membranes grafted with branched poly(N-isopropylacrylamide) chains

Temperature-responsive poly(tetrafluoroethylene) membranes grafted with branched poly(N-isopropylacrylamide) (PNIPAAm) chains have been prepared. The preparation method includes two reactions. The first step is grafts of poly(glycidylmethacrylate) (PGMA) chains to PTFE membrane surfaces through a surface-initiated free-radical polymerization, the second one is incorporation of PNIPAAm chains to PGMA segments through the addition reaction between the epoxide groups of PGMA and the amine groups of amino-terminated PNIPAAm. The chemical structures of the surface-modified PTFE membranes have been characterized with FTIR and XPS. The studies on their surface morphology have been carried out with SEM and AFM. The modified PTFE membranes display surface hydrophilicity and show a water flux of 7.6 kg m−2 h−1 at 25 °C and a 2-atm pressure drop. The water flux of the membrane at 40 °C is 34 kg m−2 h−1, which is about 4.5 folds of that measured at 25 °C, demonstrating the temperature-responsive property of the PNIPAAm-modified PTFE membrane.