Abstract:

Poly(vinylidene fluoride)(PVDF) has been considered as one of promising membrane materials due to its excellent properties such as high mechanical strength, chemical stabilityetc. and it is widely applied in the preparation of microfiltration and ultrafiltration membranes. Unfortunately, its hydrophobic nature is susceptible to fouling and remove the foulants with frequently cleaning process may pose irreversible damage to the membranes resulting in reduced membrane lifetime. Therefore, to improve the hydrophilicity and anti-fouling property, a thermo-responsive inorganic-organic nanofiber additive (palygorskite-g-poly(N-isopropylacrylamide), PGS-g-PNIPAM) was first fabricatedvia “graft from” technic and then was incorporated into PVDF matrix. 3-Methacryloxypropyl trimethoxy silane (MPS) was used for introducing ethylene groups onto the PGS surface. A series of thermo-responsive PGS-g-PNIPAM, with a wide range of grafting yields, were prepared by grafting poly(N-isopropylacrylamide) (PNIPAM) onto PGS-MPS surfaces with the free radical graft polymerization. A series of characterizations including XPS, SEM and TG were conducted and the results indicate that PNIPAM were successfully grafted onto PGS surface and the composite nanofiber owns thermo-responsiveness; the graft ratio gradually reached saturated state as the NIPAM amount increased. The PVDF/PGS-g-PNIPAM hybrid membranes were preparedvia a combination of immersion precipitation (IP) and thermally induced phase separation (TIPS) process. PGS-g-PNIPAM was incorporated into PVDF matrix and the influence of graft ratio, on membrane structures and properties was investigated in detail. The results show that the thermo-responsiveness of membranes ascended firstly and then descended lastly as the graft ratio increased and reached the maxium value at the graft ratio of 21.33% for the PGS-g-PNIPAM. The PGS-g-PNIPAM nanofibers, which uniformly dispersed in the PVDF matrix, acted as nucleating seeds and expedited the crystallization process of PVDF. As the increasing graft ratio of the PGS-g-PNIPAM, the maximum pore size, mean pore size, pure water flux (PWF) and hydrophilicity of PVDF/PGS-g-PNIPAM hybrid membranes increased. The hybrid membranes exhibited superior bovine serum albumin (BSA)-fouling resistance.

Key words: membrane, ultrafiltration, polyvinylidene fluoride, palygorskite nanofibers, permeation

摘要：

通过化学接枝法将聚(N-异丙基丙烯酰胺)(PNIPAM)接枝聚合在凹凸棒石(PGS)纳米纤维表面，制备了系列接枝率的温敏性PGS-g-PNIPAM纳米颗粒，将其与聚偏氟乙烯(PVDF)共混制备温敏性纳米复合超滤膜，深入研究PNIPAM接枝率对膜结构和性能的影响。结果表明，凹凸棒石表面PNIPAM接枝率随溶液中NIPAM单体浓度增大而增加；PGS-g-PNIPAM使复合膜中PVDF晶核变小，数目增多，膜更为疏松多孔，PVDF/PGS-g-PNIPAM膜的平均孔径在20 nm左右，膜的平均孔径和最大孔径均随凹凸棒石表面PNIPAM 接枝率的增加而增大；PVDF/PGS-g-PNIPAM膜具有温敏性，温敏开关系数随PNIPAM接枝率的增加先增强后减弱，当接枝率为21.33%时膜温敏开关系数最大，达到1.51，膜渗透通量也最大，对牛血清白蛋白具有良好的截留和抗污染性能。

关键词: 膜, 超滤, 聚偏氟乙烯, 纳米凹凸棒石, 渗透