Study On The Preparation And Performance Of PVDF-g-PNIPAAm Intelligent Membrane

N-isopropyl acrylamide (NIPAAm), a kind of typical temperature sensitivecompound, if combined with Polyvinylidene fluoride (PVDF), which is of chemicalstability, aging resistance and anti excellent ultraviolet properties, can be made intointelligent membrane with temperature sensitive characteristics, which is calledPVDF-g-PNIPAAm temperature sensitive membrane. Although it has been studied formany years, not much attention has been made on the mechanism and formingprocess of membrane formation, on which this paper will focus.In this study, a temperature-sensitive copolymer of PVDF-g-PNIPAAm wassynthesized by grafting N-isopropylacrylamide (NIPAAm) on poly(vinylidenefluoride)(PVDF) which was treated by aqueous alkali, with a free-radicalpolymerization route with2,2’-azobisisobutyronitrile (AIBN) acting as an initiator.The properties and structures of PVDF-g-PNIPAAm membranes prepared at differentreaction time, different alkaline treatment time and different content of DMF in thecoagulation bath, were studied by scanning electron microscopy (SEM) and flux ofpure water. The PVDF-g-PNIPAAm membrane was prepared by changing the contentof DMF in the coagulation bath. The ultrasonic technology was used to measure themembrane formation process.The result shows that coagulation strength can affect the properties and structureof membranes greatly. When the DMF content in the coagulation bath increases, theNIPAAm content of the membrane surface decreases. The NIPAAm content ofmembrane surface is the lowest when DMF content at15%. But when the content ofDMF goes on increasing, the NIPAAm content of the surface increases. With theDMF content increase, the membrane surface pore size and the number of poresincrease as well, the membrane cross-section structure changes from finger-like poresto sponge-like pores. The temperature sensitivity of flux shows different temperatureresponsive characteristics with the DMF content changes. Different reaction time anddifferent alkaline treatment time can affect the properties and structure of membranes.With the increase of alkaline treatment time, the grafting ratio increases at first andthen decreases. The13min alkaline treated copolymer has the maximum grafting ratio.Membrane formation time increases with the increase of alkali treatment time. Withthe increase of alkaline treatment time, the resulting membranes has more and moreholes in the surface membrane and the surface hydrophilic and water flux ofmembrane increases as well. With the increase of reaction time, the grafting ratioPVDF-g-PNIPAAm copolymers increases, the membrane formation time increases.The water flux of PVDF-g-PNIPAAm membrane which reacted for4,6,8h showstemperature sensitivity.