Superhydrophobic properties

It was found that the antioxidant activity of PANI-NFs was higher than that of conventional PANI, and that it increased with decreasing averaged diameter of the nanofibers [182], The enhanced antioxidant activity was due to the increased surface area of PANI-NFs. Conductive 3-D microstructures assembled from PANI-NFs doped with per-fluorosebacic [113,114] and perfluorooctanesulfonic acid [115], such as hollow rambutan-like spheres [115], hollow dandelion-like [113], and hollow box-like microstructures [114], exhibited superhydrophobic properties. Reversible hydrogen storage behavior of PANI-NFs at room temperature has recently been reported [437]. 

The surface depicted in Figs 2 and 3 demonstrates distinct superhydrophobic property. The APCA was determined as (150 5)°. The drop deposited on the two-scaled relief coated with chromium is depicted in Fig. 4. 

Alternatively, it is possible to apply polymer films for this purpose. Of course, such polymers must also have the ability to strongly reduce the surface free energy. Ruorine-containing polymers appear to be suitable to endow metal oxide surfaces with superhydrophobic properties, but most of them are insoluble. An exception is Teflon AF, which can be dissolved in perfluorinated solvents and applied by spin-... 

Here, we employed polymethacrylates to provide the roughened and oxidized surface of aluminium sheets with superhydrophobic properties. Polymethacrylates can be easily synthesized and their properties varied by copolymerization of methacrylate monomers that have different side chains. The correlation between the structural composition of polymethacrylates and their wetting behavior is well known from model studies carried out on thin films on smooth surfaces [19, 20], but there is no information about the wetting behavior of polymethacrylate hlms on micro-rough surfaces. We have synthesized poly(tert-butyl methacrylate) and poly(methyl methacrylate) containing different hydrophobic and hydrophilic sequences. In dependence on the polymer composition the wetting behavior was studied on polymer-coated smooth silicon wafers and rough aluminium surfaces. 

In summary, we have developed two techniques to impart superhydrophobic property to the surfaces of devices. In the first approach, oxygen plasma treatment was used to roughen the Teflon coating whose surface water contact angle could be tuned form 120° to 168° by varying the oxygen plasma treatment time. However, the application of the oxygen plasma process is limited to fluoropolymers. In the second approach, nanoimprint process was used to create nanostructures on the... 

ZnO A simple method of electrochemical deposition was adopted to prepare conductive hydrophobic ZnO thin films [504]. These ZnO films were fabricated by overpotential electrochemical deposition at room temperature, and the surface modified by a (flu-oroalkyl)silane showed superhydrophobic properties. The prepared thin films were treated with a methanol solution of hydrolyzed (heptadecafluorode-cyl)trimethoxysilane (CH30)3Si(CH2)2 (CF2)7CF3, 1.0 wt %) for 3 h and subsequently heated at 100 °C for 1 h. Wettability studies revealed that the surface of the as-prepared thin films showed a contact angle (CA) for water of 128.3 1.7°, whereas the superhydrophobic surface with a water CA of 152.0 2.0° was obtained by (fluoroalkyl) silane modification [504]. 

In an altogether different approach to improve the mechanics and introduce superhydrophobic properties, in this chapter, we are presenting work on the synthesis of flexible and superhydrophobic silica aerogels derived from methyltrimethoxysilane (MTMS) and methyltriethoxysilane (MTES) precursors and their usability as efficient sorbents for oil and hydrocarbons [18, 19]. The main objective of this chapter is to provide an overview of synthesis, characterization, and most promising areas of applications. 

Figure 5.7. Photographic image of hexane exchanged gels at the beginning (left) and at the end (middle) of the hydrophobization treatment. The gels clearly float. Contact angles above 140° of aerogels obtained in this way indicate superhydrophobic properties (right).

Figure 12.2 Values and images of the water contact angles for various surface structures [3,14]. The nanostructures in (a) and (c) exhibit superhydrophobic property...

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