Superhydrophobic polymers

FAS Perfluoroalkysilane LDPE Low density polyethylene PDMS Poly (dimethyl siloxane) 

In this chapter, a number of the top-down and the bottom-up approaches for the fabrication of superhydrophobic polymers will be presented. A brief discussion on the mechanisms of surface wettability will also be provided. 

In the production of superhydrophobic polymers, to ensure that Cassie— Baxter is the dominant state of the surface, geometric parameters should be chosen so as to ensure this state has lower energy than the Wenzel state (Patankar,2004). Surface properties that affea the stability of the Cassie—Baxter state include the dimensions and surface organization of nanoscale features 

If used, hydrophilic polymers will need to be either subjected to surface modification to impart the relevant hydrophobic functionality or coated with a thin layer of a hydrophobic polymer. 

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Genzer J, Efimenko K (2000) Creating long-lived superhydrophobic polymer surfaces through mechanically assembled monolayers. Science 290 2130-2133... 

Equation (645) shows that contact angle is a thermodynamic quantity, which can be related to the work of adhesion and interfacial free energy terms. When 6 values are small, the work of adhesion is high and considerable energy must be spent to separate the solid from the liquid. If 0 = 0°, then W L = 2yv if 0 = 90°, then W L = yLV, and if 0 = 180°, then W1L = 0, which means that no work needs to be done to separate a completely spherical mercury drop from a solid surface (or a water drop from a superhydrophobic polymer surface), and indeed these drops roll down very easily even with a 1° inclination angle of the flat substrate. 

Jan Genzer, Kirill Efimenko, Creating Long-Lived Superhydrophobic Polymer Surfaces Through Mechanically Assembled Monolayers, Science, 290 (2000), 2130-2133. 

Self-organization, honeycomb, pincushion, superhydrophobic, polymer films... 

It has been demonstrated that the preparation of superhydrophobic polymer surfaces is possible by simple plasma surface modification, either in one or two-step processes. The O2 plasma induces a variable roughness while CF4 plasma increases the roughness and creates an apolar layer. By the two-step treatment, several plasma parameters were found which allowed the preparation of superhydrophobic surfaces with controlled roughness and chemical structure. It has been shown that a superhydrophobic surface can be obtained even with a low roughness, around 20 nm. 

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. 

Han, Y., Levkin, P., Abarientos, L, Liu, H., Svec, F., and Frechet, J.M. 2010. Monolithic superhydrophobic polymer layer with photopatterned virtual channel for the separation of peptides using two-dimensional thin layer chromatography-desorption electrospray ionization mass spectrometry. Ana/. Chem., 82 2520-2528. 

Q. F. Xu, B. Mondal and A. M. Lyons, Fabricating superhydrophobic polymer surfaces with excellent abrasion resistance by a simple lamination templating method, ACS Appl. Mater. Interfaces, 3,3508-3514 (2011). 

Asthana, A., Maitra, T., Biichel, R., Tiwari, M.K., Poulikakos, D., 2014. Multifunctional superhydrophobic polymer/carbon nanocomposites graphene, carbon nanotubes, or carbon black ACS Appl. Mater. Interfaces 6. 

Feng, J., Lin, E, Zhong, M., 2010. Stretching-controUed micromolding process with etched metal surfaces as templates towards mass-producing superhydrophobic polymer films. Macromol. Mater. Eng. 295. 

Huovinen, E.,Takkunen, L., Korpela,T., Suvanto, M., Pakkanen,T.T, Pakkanen,T.A., 2014. Mechanically robust superhydrophobic polymer surfaces based on protective micropil-lars. Langmuir 30. 

Katapanagiotis, L, Manoudis, P.N., Savva, A., Panayiotou, C., 2012. Superhydrophobic polymer-particle composite films produced using wuious particle sizes. Surf. Interface Anal. 44. 

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