Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
Faraday Discuss. 2010;146:35-48; discussion 79-101, 395-401. doi: 10.1039/b925676h.
Surface roughness on different length scales is favourable for superhydrophobic behaviour of surfaces. Here we report (i) an improved synthesis for hybrid raspberry-like particles and (ii) a novel method to obtain superhydrophobic films of good mechanical stability. Polystyrene spheres with a diameter of 400 nm-1 microm are decorated with silica colloids < 100 nm in size, thus introducing surface asperities on a second length scale. To improve mechanical resistance, we then coated the polystyrene core and attached silica colloids with a smooth silica shell of 10 nm to 40 nm thickness. All three steps of this synthesis procedure can be sensitively tuned so that the average size and number of the silica colloids as well as the morphology of the resulting raspberry particles can be predicted. As the particles disperse in water, either monolayers can be prepared by dip coating or multilayers by drop casting. Although mechanically stable, the shells are porous enough to allow for leakage of molten or dissolved polystyrene from the core. In tetrahydrofuran vapour polystyrene bridges form between the particles that render the multilayer-film stable. Leaked polystyrene that masks some asperities can be removed by plasma cleaning. Surface roughness on larger scales can be tuned by the drying procedure. The films are hydrophobized by silanization with a semi-fluorinate silane.
不同长度尺度的表面粗糙度有利于表面的超疏水性。在这里，我们报告了（i）一种改进的杂化覆盆子状粒子的合成方法，以及（ii）一种获得具有良好机械稳定性的超疏水薄膜的新方法。具有 400nm-1μm 直径的聚苯乙烯球用<100nm 尺寸的二氧化硅胶体进行修饰，从而在第二长度尺度上引入表面粗糙度。为了提高机械阻力，我们然后用 10nm-40nm 厚的光滑二氧化硅壳涂覆聚苯乙烯核和附着的二氧化硅胶体。这种合成过程的所有三个步骤都可以进行敏感调节，从而可以预测二氧化硅胶体的平均大小和数量以及所得覆盆子粒子的形态。当粒子在水中分散时，单层可以通过浸涂制备，多层可以通过滴涂制备。尽管机械稳定，但壳足够多孔，可以允许从核中泄漏熔融或溶解的聚苯乙烯。在四氢呋喃蒸气中，粒子之间形成聚苯乙烯桥，使多层膜稳定。可以通过等离子体清洗去除掩盖一些粗糙度的泄漏聚苯乙烯。较大尺度的表面粗糙度可以通过干燥程序进行调节。薄膜通过用半氟化硅烷进行硅烷化来疏水性化。
