Surface Modification Of Polysulfones Porous Membranes Via Atom Transfer Radical Polymerization

In this work,Poly(phthalazinone ether sulfone ketone)(PPESK) and polysulfone(PSF), which are widely used polymers with excellent physical-chemical characteristics, were used as membrane materials.ATRP and SI-ATRP methods were employed to modify PPESK material and PSF membrane,respectively.In this paper,we mainly focused on three research projects:Firstly,we tried to graft hydrophilic poly(ethylene glycol) methyl ether methacrylate(PEGMA) onto chloromethylated PPESK main chain by ATRP aiming to obtain amphiphilic graft copolymer and use it as an additive in the blend modification of PPESK membranes which were prepared by phase inversion process.Secondly,because of ineffective removal of Cu~I in the previous study,surface modification of PSF membranes was carried out by surface-initiated ATRP(SI-ATRP).Prior to ATRP,chloromethylation of PSF was performed beforehand and the obtained CMPSF was prepared into porous membranes by phase inversion process.It was demonstrated that the benzyl chloride groups on the CMPSF membrane surface afforded effective initiators to graft the well-defined polymer brushes.In order to improve the hydrophilicity and anti-protein adsorption property of the PSF membrane,hydrophilic monomer PEGMA and GMA were grafted from CMPSF membrane to fabricate hydrophilic polymer brushes via SI-ATRP method,and further modified PSF-g-PGMA membrane by immobilizing heparin on the membrane surface to improve the hydrophilicity of the membrane. Finally,we also investigated the preparation of environment-responsive gating PSF membranes.Thermal-responsive PSF membrane was successfully prepared by grafting PNIPAAm from the CMPSF membrane surface via SI-ATRP method.Based on the research in this paper,we can draw four major conclusions:(1) The coverage of P(PEGMA) brushes on the membrane surface increased as the increase of the content of PPESK-g-P(PEGMA) in the blend membrane,resulting in improved hydrophilicity and flux;(2) The introduction of P(PEGMA) and PGMA graft chains remarkably promoted the surface hydrophilicity and anti-protein adsorption of PSF membranes,the initial contact angle decreased from 92°to 45°,and BSA adsorption decreased from 50μg/cm~2 to nearly 5μg/cm~2.By comparison of the effect of the two monomers,PEGMA evidently brought much better hydrophilicity and anti-protein adsorption ability to the PSF membranes than GMA;(3) Kinetic study of PNIPAAm SI-ATRP grafting reaction reveals a non-linear growth behavior between grafting yield(GY) and polymerization time,and the growth rate of GY decreased as the prolongation of reaction time;(4) PSF-g-PNIPAAm membrane would change from hydrophilic into hydrophobic when the temperature increased from 25℃to 50℃,and the decrease rate of contact angle became faster at 25℃as the increase of GY of PNIPAAm;The results of water flux test indicated that water flux decreased as the increase of GY of PNIPAAm,while thermal-responsive property remain almost stable; Rejection ratio test of BSA indicated that the increase of rejection ratio of BSA became slower as the increase of GY of PNIPAAm.When the GY of PNIPAAm reached to 0.37mg/cm~2,thermal-responsive property of PSF-g-PNIPAAm membrane was negligible.Thus,PSF-g-PNIPAAm with different GY showed discriminable thermal-responsive property and we could control the property of the thermal-responsive PSF membrane by tuning the GY and temperature.