Modification Of The Polysulfone Membrane Via Atom Transfer Radical Polymerization

Modifying membranes to meet the requirements of various separation has already been an important part of the study about membrane separation in recent years. Compared with the traditional modification methods, atom transfer radical polymerization(ATRP) has the advantages of activity/"controllable", mild reaction conditions, good for a wide range of monomers and so on. This article used the method of general atom transfer radical polymerization (ATRP) and the method of surface initiated atom transfer radical polymerization (SI-ATRP) to modify the commonly used polysulfone and polyethersulfone membrane by the introduction of different function monomer so that the membrane can have different separation functions. The mainly study and results of the experiments are summarized as follow:In order to make the hydrophobic membrane have a better hydrophobic property, which can be applied to organic solvent separation and other occasions, the hydrophobic fluorine-containing monomer of 2,2,2-trifluoroethyl methacrylate (TFEMA) were grafted from the chloromethylated polysulfone (CMPSF) materials via ATRP. FT-IR infrared and 19F-NMR NMR results showed that we got the grafting polymer PSF-g-PTFEMA with determined structure, Grafting yield linearly increased with reaction time. The flat blend membranes of PSF-g-PTFEMA/PSF were prepared by the wet phase inversion process. The static water contact angle of the modified membrane surface reached 81.07°from 60.17°of the pure membrane. It showed that the hydrophobicity of the membrane surface was improved by the modification.Hydrophilic modification is the mainly purpose of membrane modification. The hydrophilic monomer PEGMA was grafted from the surface of chloromethyl polyethersulfone (CMPES) hollow fiber membrane to improve the hydrophilicity of the membrane surface. FESEM and the physical structure of the membrane test results indicated the reaction mainly occured in the membrane surface. ATR-FTIR analysis showed that the PES-g-P (PEGMA) with determined structure were got on the membrane surface. GPC analysis showed the molecular weight linearly increased with the reaction and the molecular weight distribution was narrow. The grafting density on the membranes also linearly increased with the reaction time. These showed the reaction was a controlled or living process. The study also showed the hydrophilicity and anti-pollution of the membranes were significantly improved while the rejection performance was not changed.The microbes can also cause the membrane fouling. In order to improve the antibacterial properties of membranes, the functional monomers 4-vinyl pyridine (4VP) were grafted from the CMPSF membrane surface using the method of SI-ATRP to make the membrane surface have a strong complexing ability. Then the membrane surface were loaded with Cu. The effects of the monomer concentration were studied. For comparative study, the P4VP and Cu ions were directly added to the casting solution of PSF membrane using the blend method and the effects of the P4VP were studied. The section and surface morphology of the two modification membranes were scanned and the contents of Cu was measured at the same time. The contents of N were were measured to verify the content of the grafting polymer by elemental analysis. The changes of water flux and rejection of the modification membranes were investigated. The results showed that the effect of grafting was the best when the solvent amount was 20mL. The grafting density of the membrane surface reached 4.7 mg/cm2. The content of Cu can reach 3.07% through the adsorption. The E. coli inhibition rate of the membrane was 100%. The best blending membrane was got when the dosage of P4VP was 0.75% in the casting solution. Though the content of Cu can only reach 1.68%, the inhibition was almost 100%.