氧化石墨烯在芳香聚酰胺正渗透膜表面层层点击自组装及其性能研究

Aromatic polyamide (PA), one of the most widely used materials for thin-film composite forward osmosis membranes, has a high tendency to fouling, resulting in increased hydraulic resistance, decreased membrane permeability, enhanced concentration polarization, and deteriorated effluent quality. Graphene oxide is the ideal material for the membrane and membrane modification due to its high hydrophilicity, better dispersion in solvents and compatibility with polymers. To overcome the fouling proneness of the PA membranes, this project aims at layer-by-layer assembly of the graphene oxide on the PA membrane using click chemistry. First, the PA membrane is to be halogenated with sodium hypohalous (PA-X); second, halogen atoms in PA-X is to be replaced with NaN3 by SN2 nucleophilic substitution (PA-N3), thus the clickable PA is prepared, the reaction conditions, including hypohalous reaction time, pH and nucleophilic time are to be investigated in terms of the quantity of the azide groups introduced on the PA membranes; third,the clickable GO is to be prepared by introducing the azide and propargyl groups onto GO; finally, layer-by-layer assembly of the clickable GO onto the clickable PA membrane is to be conducted using click chemistry. The reaction conditions and the layers of the GO on the membrane, which affect the membrane performances (membrane permeability, solute rejection and antifouling characteristics) are to be investigated. The project highlights the combination of the technique of layer-by-layer assembly with click chemistry for the membrane surface modification, enabling the preparation and characterization of the membranes and the functionalization of GO to be conducted controllably and separately in sequences. This approach is expected to provide the membrane scientists with a new idea for the functionalization of polymeric membranes, and is promised to contribute to related membrane science, the application scopes of forward osmosis membranes would be expanded dramatically in environmental protection, separation and purification.

芳香聚酰胺(PA)是目前能够应用于正渗透过程的少数膜材料之一，但其易污染，导致膜分离性能变差；氧化石墨烯(GO)具有优异分散性、亲水性和与聚合物相容性，是优异的膜材料与膜改性材料。本项目旨在合成具有点击功能基的PA膜和GO，应用点击化学将GO层层自组装到PA正渗透膜表面，以制备功能无机纳米粒子修饰的PA正渗透膜。拟采用次卤酸钠处理膜，将卤原子引到膜上，进而卤代膜与叠氮化钠进行亲核取代制备可点击的PA膜，研究卤代时间、pH和亲核取代时间等反应条件对膜表面叠氮基引入量的影响；将炔基和叠氮基引到GO上，制备可点击的GO，研究反应条件对点击基团引入量的影响；最后将GO 层层点击自组装到PA膜，研究反应条件、自组装层数等因素等对PA膜分离性能(膜通量、截留率和抗污染性能)的影响。研究成果有望为膜分离材料功能化提供新方法，为拓展正渗透膜在环境保护和新型化工分离中的应用提供理论依据。

通过紫外光照将溴原子引入膜表面；采用SN2亲核取代反应将叠氮基团引入疏水性多孔聚丙烯膜(MPPM-N3)；利用端炔基三硫代碳酸酯和阴离子型单体2-丙烯酰胺-2-甲基丙磺酸(PAMPS)的可逆加成断裂链转移(RAFT)聚合得到具炔基PAMPS (PAMPS-)；通过Cu(I)催化点击化学反应将PAMPS引入到膜表面。支链结构可控，其制备、表征可以独立进行，为接枝链结构与组成详尽表征提供了条件。.通过威廉姆森反应合成具炔基甲氧基聚乙二醇(MPEG) MPEG (MPEG-)。通过叠氮-炔环加成反应将MPEG-接枝到MPPM-N3。MPEG接枝改性膜表面粗糙度增大、膜表面水接触角从145o降低到45o。用SPSS社会统计学分析软件对膜表面接枝链长和接枝密度与膜性能之间关系进行了相关性分析研究，发现相对于接枝密度，接枝链长对膜性能具有更显著影响，随着接枝密度和接枝链长度的增加膜性能有明显改善。.通过改进的Hummers法合成氧化石墨烯(GO)，采用氯化铵催化叠氮化钠开环GO中环氧基团，制备具叠氮基的氧化石墨烯(GO-N3)；通过GO中的羧基与炔丙胺中的氨基反应，制备了具炔基的GO (GO-)；通过点击化学法将GO层层点击自组装到MPPM-N3膜表面。GO的引入提高了MPPM膜亲水性、抗菌性和抗污染性。与未改性膜相比，5层GO改性膜水通量提升了约1.8倍，通量恢复率由43.0%增加到79.8%，而通量下降率下降了32.1%，GO改性膜的抗菌性能提升近2/3。