Preparation And Performance Of PVDF/PVDF-g-PDMAEMA Blended PH-Responsive Membrane

pH sensitive membrane is a kind of intelligent membrane which could respond to the simulation and self-regulate to the change of pH in the external environment.The conformation of polymer changes with the change of pH,which leads to the change of membrane permeability by affecting the pore size of t he membrane.pH sensitive membrane can adapt to a varity of environments and make corresponding adjustments.It has attracted extensive attention in many fields,such as drug controlled release,water treatment and chemical threshold,and pH sensitive membrane is an important part of smart membrane research.In this paper,a kind of pH sensitive graft copolymer PVDF-g-PDMAEMA was prepared by atom transfer radical polymerization（ATRP）of grafting2-（Dimethylamino）ethyl methacrylate（DMAEMA）onto polyvinylidene fluoride（PVDF）.The graft copolymer was characterized by FT-IR,TGA,¹H-NMR and XPS.The results showed that DMAEMA was successfully grafted onto PVDF molecular chain,and with the extension of reaction time,the grafting ratio of monomer increased at first,then decreased,and finally stabilized.When the polymerization time of ATRP was 8 h,the grafting rate of the graft copolymer reached the maximum value of 6.66%.PVDF/PVDF-g-PDMAEMA pH sensitive membrane was prepared by the method of immersion precipitation phase transformation.The effects of PVDF-g-PDMAEMA with different grafting rate and different amount on the properties of ultrafiltration membrane were investigated.The membranes were analyzed by XPS,and the permeability,pH sensitivity,antifouling property,porosity,mechanical properties and hydrophilicity of the membranes were tested,and the micro-morphology of the membranes was characterized by SEM.The results showed that when the pH of the solution increased,and the environ ment changed from acidic into alkaline,the polymer chain segment changed from stretching into contractive,so the permeability of the membrane was obviously enhanced,and the pH sensitivity of the membrane was proved.When the grafting ratio of the doped PVDF-g-PDMAEMA was 5.99%,and the addition amount was 1.5 wt%,the pH sensitivity of the blended membrane was the strongest.On this condition,the water flux was 891.0 L·m^-2·h^-1,the recovery rate reached 78.26%,the total pollution coefficient decreased to 58.91%,the porosity reached 87.0%,the elastic modulus was 4.164 MPa and the water contact angle was 68.2°.Therefore,the optimum polymerization time was 12 h in the synthesis process of PVDF-g-PDMAEMA,and in the preparation of membrane,the best grafting rate of PVDF-g-PDMAEMA was5.99%and the best addition amount was 1.5 wt%.