| Poly(vinylidene fluoride)(PVDF) ultrafiltration membrane was one of the most widely usedpolymer membrane materials, such as the applications in the field of water treatment, protein-separation and so on. Otherwise, the hydrophobic and easily polluted limit the application of PVDFmembranes in the field of separation. Furthermore, since the membrane pore size constraints, it canonly separate substances of a specific molecular weight. The separation of two or more differentmolecular weight substances often requires the aperture of several different filtration membraneswith multiple filters, which makes the separation process more complicated, and the cost higher.On the basis of the analysis of temperature-sensitive membrane and the preparation methods ofmembrane, a temperature-sensitive membrane was prepared by blended with the temperature-sensitive copolymer.In this paper, poly(N-isopropylacrylamide), poly(poly(ethylene glycol)monomethacrylate),tert-butanol and2,2’-Azobis(2-methylpropionitrile)(AIBN) were used as the main material tosynthesize a series of different temperature-sensitive poly-N-isopropyl acrylamide-co-polyethyleneglycol methyl methacrylates (NPGs) containing different mass ratios of N-isopropyl acrylamide(NIPAAm) and poly(ethylene glycol) methacrylate (PEGMA). GPC,1HNMR, FTIR and UV-viswere conducted to characterize NPGs. The influence of reaction condition such as ratio of thereactants, solvent of polymerization reaction, reaction temperature and time were investigated. Asthe results shown, when copolymerization of NIPAAm with PEGMA was carried out at88℃for6h in tert-butanol.2,2’-Azobis (2-methylpropionitrile)(3%relative to monomers) as an initiatorwas the best reaction effect. The copolymers have different LCSTs synthesized by changing themass ratio of the two monomers.Then the NPGs were blended with poly(vinylidene fluoride)(PVDF) to prepare ultrafiltrationmembranes which have temperature-sensitivity, higher hydrophilicity. Experiment was tested toresearch the modification effect of temperature-sensitivity copolymer NPGs with different ratio ofthe two monomers and the modification effect of different content of NPGs in the blendmembranes. The mixing compatibility between temperature-sensitivity copolymer NPGs andPVDF were determined by differential scanning calorimeter (DSC). Scanning electron microscopy(SEM) and atomic force microscopy (AFM) were used to observe the surface and cross section morphology of poly(vinylidene fluoride) and the blend ultrafiltration membranes. With PEGMAcontent increasing in NPGs, the structure of pure membrane and blended membranes changedfrom typical asymmetric morphology with short finger-like pores to macrovoid. The angle-meterwas used to study the hydrophilicity of the ultrafiltration membrane surface. The contact angle ofthe blended ultrafiltration membranes decreased comparable to the value of the pure PVDF. Thewater fluxes of the membranes at different temperature and the rejection measurements to differentmolecular substances were conducted out to research the temperature-sensitivity of blendedultrafiltration membranes. With the temperature or PEGMA content increasing, the water flux bothincreased obviously. The rejection of the same membrane to different molecular weight substanceschanged greatly with temperature changing from10C to60C, which made it possible to separatesubstances by controlling temperature. Anti-pollution experiment were tested to compare the anti-pollution of the pure PVDF and blended membranes.Finally, the temperature-sensitive copolymer which have a perfect blended effect was selectedto modified the PVDF membrane. The properties of the casting solutions and the influence of thecopolymer content and the coagulation bath temperature were investigated. The results showed thatthe coagulation bath temperature influenced the membrane formation process greatly．... |
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