Influence of Coagulant Temperature on the Membrane Formation Process and Properties of PVDF-g-PNIPAAm Temperature-sensitive Membranes

The copolymer of poly (vinylidene fluoride) grafting poly (N-isopropylaerylamide) (PVDF-g-PNIPAAm) was synthesized and its flat sheet membranes were prepared. The influence of coagulant temperature on membrane formation kinetics was studied by the ultrasonic time-domain reflectometry(UTDR). Based on the membrane formation kinetics, the influence of coagulant temperature on the structure and performance of PVDF-g-PNIPAAm membrane was studied. The results show that the coagulant temperature influences the membrane formation process greatly. The liquid-liquid dimixing dominates the dimixing process at different coagulant temperature. The needed membrane formation time of PVDF-g-PNIPAAm prepared at 30 degrees C was the longest and that of the membrane prepared at 40 degrees C was the shortest. The crystal properties of the PVDF-g-PNIPAAm membrane are dominated by the corresponding PVDF structure. The higher the coagulant temperature, the lower the degree of crystallinity is. The NIPAAm content on the surface of PVDF-g-PNIPAAm membrane is much higher than that of the PVDF-g-PNIPAAm copolymer. The NIPAAm content on the surface of PVDF-g-PNIPAAm membrane prepared at 30 degrees C is the highest. All the membranes presents finger-like pores. The membranes prepared at 30 degrees C has the largest pores and the highest porosity. The water flux of membrane prepared at 25 degrees C showed obvious temperature sensitivity and increased intensively at about 30 degrees C.