Studies On Surface Modification And Properties Of Aromatic Polymer Anti-fouling Membranes

In the process of introducing active radical chloromethyl（-CH₂Cl） groups in bulk modification, the utilization of catalyst such as SnCl4, ZnCl2 will cause damage to environment, and the organic phase solvent such as ClCH₂OCH₃, CHCl3 are harmful to human.Chloromethylation of poly（aryl ether ketone）（PEK-C） ultrafiltration membrane and polysulfone（PSF） ultrafiltration membrane was performed on the surface by phase transfer catalyst（sulfonic ammonium）, which is hypotoxicity.Zwitterionic polymer of sulfobetaine methacrylate（SBMA） was grafted from PEK-C membrane and PSF membrane via surface-initiated atom transfer radical polymerization（SI-ATRP）. The modified membranes showed character of hydrophilicity and anti-foling. In this study, paraformaldehyde, sulfonic ammonium, hydrochloric acid were used to perform chloromethylation of PEK-C membrane and PSF membrane,-CH₂ Cl groups were initiated on the surface of membrane. The –CH₂Cl groups on membrane surface as SI-ATRP initiator, introduced SBMA on the surface of PEK-C membrane and PSF membrane. The polysulfone-graft-sulfobetaine methacrylate（PSF-g-PSBMA） membrane and the poly（aryl ether ketone）-graft-sulfobetaine methacrylate（PEK-C-g-PSBMA） membrane were characterized by scanning electron microscopy（SEM）, X-ray photoelectron spectroscopy（XPS） was used to track the surface composition of PSF, PSF-Cl, PSF-g-PSBMA, PEK-C, PEK-C-Cl, PEK-C-g-PSBMA membranes, attenuated total reflectance-Flourier transform infrared spectra（FTIR） was used to confirmed SBMA was grafted on the ultrafiltration membrane for further clarification. The study found that under such condition: chloromethylation temperature 70℃, chloromethylation time 6 h, paraformaldehyde 2.0 g, catalyst 0.15 g, hydrochloric acid 30 mL, ATRP temperature 70 ℃, ATRP time 6 h, the concentration of SBMA 1.5 mol/L, the modified PEK-C membrane contact angle is minimum, which is decreased 40°compared with pristine PEK-C membrane; chloromethylation temperature 70 ℃, chloromethylation time 3 h, paraformaldehyde 1.5 g, catalyst 0.05 g, hydrochloric acid 40 mL, ATRP temperature 70 ℃, ATRP time 6 h, the concentration of SBMA 1.5 mol/L, the modified PSF membrane contact angle is minimum, which is decreased 50° compared with pristine PSF membrane, which exhibited excellent hydrophlicity. The study explored the effect of chloromethylation time and ATRP time on the membrane property（pure water flux, rejection ratio, flux recovery ratio）. In the following experiments, the chloromethylation time and ATRP time of PEK-C membrane were set as 6 h and 6 h; the chloromethylation time and ATRP time of PSF membrane were set as 1 h and 6 h. Under the optional conditions, the flux recovery ratio of both membranes were over 90%. Protein adsorption experiment was carried out with（bovine serum albumin） BSA solution, the result indicated that the adsorption values of both membranes were evidencly decreased with the increase of the ATRP time. Membrane anti-bacterria test was conducted with E.coli, the result showed that both modified membrane had antibacterial property. Much bacteria were attached on the surface of unmodified membranes. With ATRP time prolonging, the number of E.coli was reduced on the modified membrane surface. Almost no bacteria were detected on the surface of ATRP time 9 h.In this study, we obtained the modified PEK-C membrane and modified PSF membrane via chloromethylation and SI-ATRP, the two modified membrane showed excellent property of hydrophilicity and antifouling. This provide a theoretical basis for application of PEK-C and PSF membrane, such as desalination, wastewater treatment, food industry and other fields.