Preparation Of Novel Thermo-and PH-sensitive Membranes By Surface Photo-grafting Polymerization

In this paper, surface photo-grafting polymerization was conducted on the surface of three kinds of membranes, the micro-filtration membranes of Nylon, CPP films, the micro-filtration membranes of polypropylene. By choosing the grafting functional monomers, three kinds of novel environment-sensitive membranes have been prepared.Novel thermo-sensitive membranes were prepared by photo-grafting N,N-diethylacrylamide (NDEA) onto the micro-filtration membranes of Nylon with benzophenone (BP) as an initiator. Grafted membranes with a wide range of grafting yield were obtained through varying the grafting conditions, including UV intensity, the irradiation time and the mole ratio of initiator. The existence of the grafted layers of poly(N,N-diethylacrylamide) (PNDEA) was confirmed by ATR-FTIR and ESCA measurements. The SEM images indicated that the grafted polymers existed mainly on the top surface of the membranes and inside the pores rather than on the backside. The water flow rate of the membranes with the appropriate grafting yield increased sharply with increasing temperature to the range of 30-35°C near the lower critical solution temperature (LCST), which revealed the performance of the thermo-sensitivity after grafting modification. The influence of grafting yield on the filtration performance of the membranes was also investigated. The mechanism of thermo-sensitivity is that the grafted PNDEA chains exist on the expanded configuration below the LCST while have a collapsed configuration above the LCST, which could be intuitively observed by AFM. In the vicinity of the LCST, a slight temperature change will induce a sharp and rapid swelling-deswelling transition of the PNDEA chain. Consequently, the grafted PNDEA chain will act as a sensor or a chemical valve to...