Wettability superhydrophobic

D nano-stmctured arrays, wettability, superhydrophobicity, colloidal monolayer crystal... 

The contact angle is 0ca < 90° when the solid is hydrophilic (so-called high energy solid) and the water wets such a solid well it is usually < 30° and approaches zero when the water completely spreads over the solid. For hydrophobic solids (so-called low energy solids) 0ca > 90° and may have values up to 150° for so-called superhydrophobic surfaces such as specially prepared (non-wettable) fluorohydrocarbons. There exists some hysteresis (amounting typically up to 10°) between the contact... 

The wettability of solid surfaces is a veiy important properly of surface chemistiy, which is controlled by both the chemical composition and the geometrical microsttuc-ture of surface [21-23], When a liquid droplet contacts a solid surface, it will sptead or remain as droplet with the formation of angle between the liquid and solid phases. Contact angle (CA) measurements are widely used to characterize the wettability of solid surface. Surface with a water CA greater than 150° is usually called superhydrophobic surface. On the other hand, when the CA is lower than 5°, it is called superhy-drophilic surface. Fabrication of these surfaces has attracted considerable interest for both fundamental research and practical studies [23-25]. 

In order to better quantify what affects the liquid response upon impact, Duez et al. [47] systematically measured the threshold velocity U associated with the onset of air entrainment as a function of the numerous experimental parameters sphere wettability, sphere diameter, liquid characteristics (dynamic viscosity, surface tension) or gas characteristics (nature, pressure)— We concentrate first on the role of surface wettability. Figure 4 shows the evolution off/ with the static contact angle 9q on the sphere. As already mentioned, U strongly depends on 9q, particularly in the non-wethng domain 9q > 90°) where U starts from around 7 m/s to become vanishingly small for superhydrophobic surfaces with 9q 180°. In this last case, an air cavity is always created during impact, whatever the sphere velocity. 

Surface wettability is a significant factor in determining the physical and chemical properties of materials. Superhydrophobic surfaces have found application in a variety of settings, including self-cleaning surfaces, prevention of snow sticking, oxidation and heat conduction processes and others [1-3], Considering the... 

Superhydrophobic surfaces based on poly(methyl methacrylate) (PMMA) with flower-like structures were prepared by controlling the aminolysis reaction of surface ester groups and the surface morphology of PMMA. The effects of the aminolysis time and the processing temperature in stearic acid solution on the surface wettability and surface morphology were examined in detail. The combination of rough surface morphology and the presence of hydrophobic carbon chtiins on the top layer was responsible for the super-hydrophobicity. 

As mentioned above, the aminolysis reaction is a crucial step for forming superhydrophobic surfaces, and the reaction temperature between amino groups and stearic acid is another key factor. So, the effect of the reaction temperature on the surface morphology and surface wettability of modified PMMA surface was also examined. All samples for this examination were immersed in ethylenediamine-anhydrous ethanol mixture for 3 h before they were modified with stearic acid. As shown in Fig. 4, the temperature at which PMMA plates were processed in stearic... 

The experiment indicates that, in principle, this technique could be used to create a full length wettability gradient from superhydrophobic to superhydrophilic on a single substrate which, to our knowledge, has been rarely achieved so far [38-40],... 

Wettability and Superhydrophobicity of 2-D Ordered Nano-structured Arrays Based on Colloidal Monolayers... 

Based on colloidal monolayers of polystyrene spheres, we have prepared various two-dimensional nano-structured arrays by solution routes and electrodeposition. Many ordered structured arrays generated using these methods are of surface roughness on the nano- and micro-scales, and could be superhydrophobic or superhydrophilic. The nano-devices based on such nano-structured arrays would be waterproof and selfcleaning, in addition to their special device functions. In this article, taking silica, ZnO and gold as examples of the insulators, semiconductors and metals, respectively, we report some of our recent results to demonstrate controlled wettability and superhydrophobicity of two-dimensional ordered nano-stmctured arrays with centimeter square-size based on colloidal monolayers. 

These silica nanoparticles generate surface roughness on the polybenzoxazine nanocomposite film, possessing both micro- and nanoscale binary structures. In addition, its appropriate chemical structure allows for reversible wettability operation. The as-prepared superhydrophobic surface is not wettable by pure water. Mohammad et al. [13] reported that aqueous solutions of various surfactants were able to wet a superhydrophobic surface since these surfactants reduced the siuface tension of the solutions. Soeno and co-workers [14] also reported wetting of their superhydrophobic surfaces with a water/ethanol mixture. In this study, ethanol was chosen to reduce the surface tension of the solvent and shift the superhydrophobic polymer film into wettable film through a relatively milder condition. 

The combination of changes in surface chemistry and surface roughness can enhance stimuli-responsive wettability. Here, we have presented a simple one-step method to prepare apolybenzoxazine-silica nanoparticle film, displaying reversible wettability via a solvent treatment. The difference in the water CAs of the same composite film, before and after solvent treatment was achieved to be 19° with silica content of 120 phr. Compared with a traditional superhydrophobic surface, the as-prepared film can be modified to show not only hydrophobicity but also a high adhesion force with water. Our results are considered to be significant in terms of their importance to academic research and industrial applications. 

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