纳米银在Breath Figure方法制备多孔膜过程中的界面作用

利用原位还原法，我们实现了在聚合物基质中合成纳米银颗粒。同时在用Breath Figure方法制备多孔膜的过程中，我们发现纳米银颗粒可以诱导多孔结构在聚合物表面形成。Breath Figure (BF) ，又称“水辅助法”，在有机溶剂挥发的过程中，聚合物溶液表面温度迅速降低，潮湿空气中的水滴会凝结在膜表面，并形成规整排列，待有机溶剂和膜表面的水滴挥发完全，规整如蜂巢般的孔洞结构就会留在聚合物膜表面。纳米银在此过程中，会吸附和聚集在水滴和聚合物溶液的界面上，引起铺展系数的变化，同时形成一种机械阻挡层，可以使水滴稳定在气液界面，同时阻止了水滴间的互相融合。同时研究发现，纳米银在BF中的界面效应具有湿度依赖性和聚合物依赖性。纳米银的加入，可以使BF方法更广泛的应用于多种聚合物，同时扩展了BF的反应条件。这种纳米银修饰的多孔聚合物表面也将会有更多潜在的应用前景。

Xiaoli Jiang, Xuefeng Zhou, Yu Zhang, Tianzhu Zhang, Zhirui Guo, and Ning Gu.Interfacial Effects of In Situ-Synthesized Ag Nanoparticles on Breath Figures. Langmuir, 2010, 26 (4), pp 2477–2483

Figure 2. AFM images of polyurethane films. (A) The pure PU film and (B) Ag nanoparticle-added PU film obtained at 90%RH. (C) The pure PU film and (D) Ag nanoparticle-added PU film obtained at 30%RH.

Figure 5. AFM images of poly (L-lactic acid) films. (A) The pure PLLA film and (B) Ag nanoparticle-added PU film obtained at 90%RH (inset: the distribution of hole size). (C) The pure PLLA film and (D) Ag nanoparticle-added PU film obtained at 30%RH.

Figure 6. (A) Cross-sectional schematic diagram of nanoparticle assembly at the water droplet-solution interface during BF formation. (B)AFM images of Ag/PU films cast at 30%RH. In the magnified image (C), Ag nanoparticles can be seen embedding on the caves on the PU film. (D and E) AFM images of Ag/PLLA films cast at 90%RH.

Figure 8. Cross-sectional schematic diagram of water droplets stabilized at the interface during breath-figure formation. (a)Wetting behavior of the water droplet. (b)When PU is in THF at 30% RH, the presence of Ag nanoparticles in the polymer forms a mechanically resistant layer preventing the water droplet from dissolving in the polymer solution. (c) As for the case of PLLA in CHCl3 at 90%RH, the water droplets grow fast to a large volume and immerse deeply into the polymer solution. With the addition of Ag nanoparticles, S increases by the reduction of the contact angle of the Ag/PLLA film. Therefore, the water droplet spreads over a larger area on the interface and immerses less into the solution.