Hydrophilic Modification Of Porous Polymer Membranes

In the present thesis, poly(vinylidene fluoride) (PVDF) and polyethersulfone (PES) porous membranes were prepared via phase inversion process to improve the hydrophilicity of the membranes. The structure and properties of membrane were characterized in order to verify the efficiency of different method used in modifying the hydrophilicity of membranes.Amphiphilic Block Copolymer PTFE-b-PEO (FSO) was used as additive in the preparation of PVDF phase inversion membrane on the basis of principium that the enrichment of hydrophilic PEO segments endow membrane with hydrophilicity, and the strong interaction between hydrophobic fluorinated segments and PVDF improve the stability of the copolymer in membrane. The structure, properties, and simulated application of the PVDF/FSO blend membrane demonstrated that this scheme were scientifically reasonable. An amount of 30wt% FSO-added generated a decrease of water contact angle to below 10° after 15 sec, and the water flux was 1970.10 L/h*m².In order to prepare hydrophilic PES porous membrane, the block copolymer PEO-PPO-PEO (Ep1 Ep2) and sulfonated poly(ether sulfone) (SPES) were served as hydrophilic modifiers, and polyvinylpyrrolidone (PVP K90) nano-TiO₂ Tween-80 and H₂O were selected as additives. An amount of 30wt% Ep1-added generated a decrease of water contact angle to below 10° after 150 sec, and the water flux was 1690.47 L/h*m². However, the results demonstrated that PES membranes modified by SPES are better than which dealed with PEO-PPO-PEO.Graft polymerization of acrylate acid (AAc) and N-Vinyl-2-pyrrolidone(NVP) onto PVDF membrane surfaces was achieved using corona discharge in atmosphere ambience as an activation process followed by polymerization of AAc/NVP in aqueous solution. The grafting of PAAc/NVP on PVDF membrane was confirmed by FT-IR/ATR and XPS analysis. The hydrophilicity of grafted membrane enhanced with the increase of corona treatment time and AAc/NVP solution concentration. On the same conditions for membrane preparation, the modifying efficiency of NVPgrafted to PVDF membranes are better than AAc does, and the water contact angle of NVP-grafted PVDF membrane was 45.7°.