Modification PVDF Membrane Via Amphiphilic Copolymer And Membrane Surface Zwitterionicalization

Poly(vinylidene fluoride)(PVDF) is a kind of semi-crystalline polymer, which has hasexcellent performance such as chemical stability, corrosion resistance, heat resistance, radiationresistance, aging resistance et al. In addition, it also has good mechanical property and membrane-forming property, which makes PVDF to be used in water treatment membrane widely. However,the strong hydrophobicity of PVDF leads to stronger driving force in water treatment process andeasily to be contaminated, which decreased the membrane service life and increase membraneoperate cost. Based on the contamination mechanism, Based on the mechanism of membranefouling, improving the hydrophilicity of membrane is an important approach to improve themembrane fouling resistance.The method of blending with hydrophilic copolymer is easily operating and producing withlarge scale. The hydrophilic molecular chains of amphiphilic copolymers would migratespontaneously to the surface of the membrane forming a hydrophilic layer with long-term stability,which results in improvement of the wetting properties and fouling resistance significantly.Furthermore, because of the super capacity of bind water molecules and resistance ofnonspecific protein adsorption, zwitterionic polymers have received great attention in anti-foulingmodification fields. And byzwitterionicalization amphiphilic/PVDF blend membrane preparedbefore could On only study the effect of zwitterionicalization on membrane properties but alsocompare modification effect of both kinds of modified membranes. The effects of amphiphilicpolymer and zwitterionicalization on PVDF membrane were characterized by water contact angle,water flux, BSA rejection rate, recovery rate, structural, mechanical properties and elementsdistribution of the membrane surface. (1) A kind of macromolecular initiator based on polydimethylsiloxane(PDMS) was used toinitiate the reaction of N, N-dimethylacrylamide (DMAA) monomers via a typical atom transferradical polymerization (ATRP). The product was a kind of PDMS based amphiphilic blockcopolymer with different PDMAA chain length and well controlled molecular weight andmolecular weight distribution. PVDF/PDMAA-PDMS-PDMAA blend membranes were preparedby blending copolymers with PVDF dope through non-solvent induced phase separation (NIPS)process. The result is that, by adding amphiphilic copolymer, blend membranes hydrophilic ity,BSA rejection rate and recovery rate improved.(2)Amphiphilic copolymer PDMAEMA-PDMS-PDMAEMA was prepared as precursorzwitterionic polymer by ATRP polymerization. Blend membranes by adding PDMAEMA-PDMS-PDMAEMA was prepared by NIPS process. Studies have shown that, amphiphilic copolymer hadsignificant effect on membrane morphology, i.e. membrane surface pores and roughness.Membrane hydrophilicility, flux, BSA retention and recovery rates all have obv ious improvement,especially pure water flux from105L/m2h increased to378L/m2h, retention rate from38.2%increased to77%, indicating that the blend membrane have significant improvement oncomprehensive property.(3) Surface zwitterionicilized membrane was prepared via quaternization reaction by3-BPAand PDMAEMA-PDMS-PDMAEMA/PVDF membrane. Studies have foundthat,zwitterionicalization also have a obvious on membrane morphology like more roughnesssurface and more compact structure. Compared to amphiphilic polymer blend membranes, theperformance of surfacezwitterionicalization membrane has better comprehensive performance,especially BSA rejection rate and recovery rate could be reach93.7%and88%, respectively,which were much higher than blend membrane and pure membrane.