聚偏氟乙烯纳米多孔膜结构调控及离子传递特性

Structure regulation and ion transport characteristics of polyvinylidene fluoride nanoporous membranes

在纳微米尺度调控膜孔结构对发展高性能膜分离材料具有重要意义。使用半结晶性高分子材料聚偏氟乙烯(PVDF),利用非溶剂诱导相分离(NIPS)、蒸汽诱导相分离(VIPS)、溶剂蒸发诱导相分离(EIPS)方法,成功制备了不同形貌的多孔膜。提出了根据聚合物的结晶生长机制调控膜孔结构概念,根据溶剂蒸发时间调控结晶生长。利用SEM和BET对膜孔形貌进行表征,XRD和DSC对结晶进行检测,氢离子(H+)和四价钒离子(VO2+)以及其他常用离子的扩散系数表征传质特性。在溶剂蒸发诱导结晶的过程中,随着溶剂蒸发时间的延长,膜断面的球晶比例逐渐增加,最后至球晶完全融合,膜孔结构发生了显著变化,且膜的结晶度和结晶形态随之发生变化,离子选择性能随膜孔尺寸减小而逐渐增大。

A series of polyvinylidene fluoride（PVDF） porous membranes with different pore structures were prepared from PVDF and sodium allyl sulfonate（SAS） via various phase inversion methods, such as non-solvent induced phase separation（NIPS）, vapor induced phase separation（VIPS）, and solvent evaporation induced phase separation（EIPS）. A concept for membrane structure regulation was proposed on the basis of growth mechanism of polymer crystalline which controlled crystal growth by solvent evaporation time. The membrane was characterized by scanning electron microscopy（SEM）, Brunner-Emmet-Teller（BET）, X-ray diffraction（XRD）, differential scanning calorimetry（DSC）, as well as permeability of protons（H~＋）, tetravalent vanadium ions（VO^（2＋））, and other ions. With the increase of solvent evaporation time, spherulites in cross-sectioned membrane was increased gradually till all spherulites grew into each other, such that membrane porous structure changed significantly as well as membrane crystalline percentage and morphology were altered. The decreased membrane pore size improved selectivity for H~＋ relative to VO^（2＋） from 12 to 73, which demonstrated high separation properties of the naonporous membrane.