SMA-g-PGE Brush Copolymer Synthesis And Hydrophilic Modification Of PVDF Membrane With SMA-g-PEG

Poly(vinylidene fluoride)(PVDF) membranes are widely used in membrane separation technology, because of its excellent chemical stability and mechanical properties. However, due to its hydrophobicity, PVDF membrane is likely to be contaminated in the membrane separation process. In this case, the membrane flux will decline, simultaneously the separation efficiency and service life will be affected. Styrene / maleic anhydride-grafted polyethylene glycol(SMA-g-PEG) is an amphiphilic copolymer with a brush- like structure. It has a special functional groups and good hydrophilicity. Hydrophobic end of the SMA-g-PEG will be attached to the PVDF membrane surface, while the hydrophilic end of the outward, when blend with PVDF to make blend UF. This will improve the hydrophilic properties of PVDF membrane.Styrene / maleic anhydride(SMA) is reacted with polyethylene glycol(PEG), resulting brush amphiphilic copolymer SMA-g-PEG, under certain conditions. Analysis the functional groups of the SMA- g-PEG by IR spectra. Then, analyze the compatibility of PVDF / SMA- g-PEG system using solubility parameter method, a co-solvent method, viscosity method and phase diagrams. Analysts believe that the PVDF / SMA- g-PEG system is partially compatible system mixed SMA- g-PEG copolymer and PVDF in different proportions, to prepare blend ultrafiltration membranes, and characterized blend films.The result of film flux and film contact angle test proved that the addition of amphiphilic copolymer SMA-g-PEG can improve the hydrophilicity of PVDF ultrafiltration membrane. For example, the water flux of blend membrane is 120 L/m2·h, when SMA- g-PEG adding proportion is 10%, but the water flux of the pure PVDF membrane is only 54 L/m2·h. The water flux of blend membrane is increased from 120 L/m2·h to 636 L/m2·h, when SMA- g-PEG adding proportion is from 10% to 40%. At the same time, the contact angle of the membrane decreased, such as the time of 90 s, the contact angle of the pure PVDF membrane is 78 °, and the blend membrane containing 10% SMA- g-PEG decreased to 65°. Discovered by SEM scanning and mechanical tests that, larger aperture, wrinkles, overlapping and dents appeared on PVDF membrane surface when add the SMA- g-PEG. Moreover, tensile strength of the membrane was 0.37 MPa, which lower than the tensile strength of pure PVDF membrane 0.57 MPa, when SMA-g-PEG adding proportion is 10%. At the same time, elongation at break decreased from 23.71% of pure PVDF membrane to 10.12 %. Apparently, the tensile strength of PVDF membrane and the elongation at break both decreased with the addition of SMA-g-PEG.