Superhydrophilicity templation

Figure 17.6 FESEM images of polypyrrole nanofIber network (a) Low magnification image and (b) edge view of the polypyrrole nanofiber network. High magnification images of polypyrrole nanofiber network formed at (c) 120 s and (d) 1 b. (Reprinted with permission from Macromolecules, Template-Free Electrochemical Synthesis of Superhydrophilic Polypyrrole Nano fiber Network by J.F. Zhang, C. M. Li, S.J. Baoetal.,41, 19, 7053-7057. Copyright (2008) American Chemical Society)...

According to Wenzel s equation, obviously, high roughness can enhance the hydrophilicity of a native hydrophilic surface. In our study, such porous film is much rougher than relatively flat surface obtained without using template, so this model can explain why our as-synthesized films show superhydrophilicity with a CA about 5°. After modification with a lower surface free energy material, the air can be trapped in such ordered pore array, and hence a composite surface composed of air and pore array is formed. The measurements show that the surface is superhydrophobic with water CA of 154°. In this case, the Cassie equation is applicable. Based on a simplified model, as schematically illustrated in Fig. 6, the relationship... 

Kang, C., Lu, H.,Yuan, S., Hong, D.,Yan, K., Liang, B., 2012. Superhydrophilicity/superhydrophobicity of nickel micro-arrays fabricated by electroless deposition on an etched porous aluminum template. Chem. Eng.J. 203, 1. 

---