法向梯度浸润性多孔膜的构筑及液体单向驱动研究

Gradient wettability materials, which exhibit great application potentialities in droplet driving, fluid controlling and so on for its unique properties, has become a hotspot in the research field of functional interface materials. In gas/liquid/solid three-phase system, materials with gradient wettability in two-dimensional plane direction have been successfully fabricated and used in many areas. However, harnessing the gradient wettability in the normal direction is seldom achieved in liquid/liquid/solid three-phase system. In this work, an important breakthrough will be made in the study of gradient wettability materials. The research on gradient wettability materials in plane direction based on gas/liquid/solid system will be extended to the normal direction in liquid/liquid/solid system. Electrospinning has been applied to fabricate the porous fibrous films with gradient wettability in normal direction. By regulating and matching the degree of wettability gradient in the normal direction, the unidirectional water penetration under oil and unidirectional oil penetration under water will be achieved. Furthermore, the mechanism and control rules of the unidirectional liquid-penetration driven by the gradient wettability in liquid phase, combined with the relationships of unidirectional liquid-penetration, liquid surface tensions and the normal directional gradient wettability are delved deeply. It will provide a facile method and lay the foundation to the fabrication and research on functional gradient wettability materials that can be applied in separation of chemical reactants and products as well as other fields.

梯度浸润性材料以其独特的性能和在液滴驱动、微流体流控等领域展现出的极大应用潜力成为近年来功能界面材料领域研究的热点。目前基于气/液/固体系材料平面水平方向梯度浸润性材料被成功制备出来并得到应用。然而，对于液/液/固体系垂直于材料表面的法向方向梯度浸润性材料的研究极少。本课题拟在传统梯度浸润性材料研究基础上，将气/液/固体系材料平面方向梯度浸润性拓展至液/液/固体系材料法向方向，采用静电纺丝法构筑液相下具有法向梯度浸润性的多孔膜材料，探究其法向方向浸润性梯度的有效构筑和调控。在此基础上，实现法向梯度浸润性驱动水相下不同表面张力油的单向透过及不同表面张力油相下水的单向透过。进一步研究液下材料法向梯度浸润性驱动液体单向透过的趋势和规律，揭示液体单向透过、液体表面张力与法向梯度浸润性之间的关联和相互作用，为应用于化学反应中反应物及产物分离等领域的梯度浸润性材料的构筑和研究奠定基础。

本项目在资助周期中主要进行了三方面的研究工作，包括：多级结构微/纳米纤维膜的静电纺丝高效构筑、浸润性转变调控，探究多级结构微/纳米材料结构对污水中重金属离子(Cu(II))去除性能的影响；成功构筑了具有法向浸润性梯度(差异)的复合多孔纤维膜材料，获得高效便捷调控其法向浸润性梯度的实验参数，探究其驱动液体单向透过机理，并将其应用在空气中微小水滴收集领域。研究多孔膜材料法向浸润性差异、膜厚度法向方向结构调控引起的定向毛细力作用对集水性能影响；法向浸润性差异膜材料的制备及其驱动不同表面张力液体(油)的单向透过、油水分离的应用研究。.通过一系列研究，获得了通过静电纺丝法高效构筑多级结构微/纳米纤维膜的关键影响因素及材料结构调控对材料浸润性和在水溶液中重金属铜离子吸附去除性能的作用机制及影响；提出采用“逐层静电纺丝法”制备疏水/亲水聚丙烯腈(PAN)Janus法向浸润性差异复合多孔纤维膜材料，调控和匹配复合膜孔径，发现疏水大孔和亲水小孔构成的Janus电纺PAN复合多孔膜不仅具有疏水-亲水浸润性差异，同时由于孔径差异诱导形成定向毛细力驱动微小水滴高效从疏水向亲水层透过，将其应用于空气中水滴收集领域，其水的收集效率是无定向毛细力作用Janus多孔膜的1.7倍；构筑疏水/疏油-疏水/亲油的(聚偏氯乙烯-六氟丙烯)-(聚偏氯乙烯-六氟丙烯+氟硅烷)(PVDF-HFP-(PVDF-HFP+FAS))，调控PVDF-HFP+FAS中FAS的比例可以实现不同表面张力液体(油)的浸润性调控(亲油或疏油)，将其应用于油水分离中明显提高油水分离效率。同时，构筑疏油/亲油PVDF-HFP+FAS/钢丝网构成的复合膜，改变起主要疏油作用的FAS添加量，能够实现不同表面张力液体(油)的单向驱动透过。本研究对多级结构微/纳米纤维膜的高效构筑及应用、法向梯度浸润性复合多孔纤维膜结构与液体表面张力、材料法向浸润性梯度与液体单向透过性能之间的关联、相互影响和作用机理做了一定的基础研究工作，将为液体单向传输、分离膜材料的设计、构筑及性能调控提供理论参考和支持。