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Superhydrophobic Organic-Inorganic Nanohybrids
Published in Chang-Sik Ha, Saravanan Nagappan, Hydrophobic and Superhydrophobic Organic-Inorganic Nanohybrids, 2018
Chang-Sik Ha, Saravanan Nagappan
A nanofibrous mat was developed using a colloidal electrospinning technique for membrane distillation (MD) [111]. A hydrophobic silica nanoparticle dispersion was prepared by modifying the surface properties of silica nanoparticles (40 nm) with a hydrophobic silane coupling agent or surface modifier (octadecyltrichlorosilane, OTS). A colloidal solution was prepared by dispersing the OTS-modified silica nanoparticles (18 wt%) in DMF. Similarly, a polyvinylidene (PVDF, 18 wt%) solution was also prepared in DMF. The OTS-silica nanoparticles/DMF dispersion was added to the PVDF/DMF dispersion at a 1:2 ratio and mixed strongly to produce a homogenized dispersion that was used for the fabrication of a nanofibrous scaffold. The nanofibrous scaffold showed a micronanohierarchical surface morphology and superhydrophobicity due to the combination of inorganic nanoparticles and organic PVDF.
Hydrophobic and Hydrophilic Polymer Coatings
Published in Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai, Suchart Siengchin, Polymer Coatings, 2020
Sanjay Remanan, Harikrishnan Pulikkalparambil, Sanjay Mavinkere Rangappa, Suchart Siengchin, Jyotishkumar Parameswaranpillai, Narayan Chandra Das
The porous polymeric coating prepared by photo- and thermal initiation results in highly superhydrophobic polymers with a very high contact angle (>170°) (Levkin, Svec, and Fréchet 2009). Porous coating of poly(butyl methacrylate-co-ethylene dimethacrylate) and poly(styrene-co-divinylbenzene) is two such examples and shows ultraphobicity. The ultraphobic nature arises from the presence of porogens in the polymerization system. Porogens are the solvents added to the polymerization reaction, which leads to phase separation when the growing cross-linked structure gains a critical size. This phase separation results in the formation of a highly porous structure from globules that have a hierarchical surface, which helps in achieving the superhydrophobicity. Genzer and Efimenko developed mechanically assembled monolayers from an elastomeric material, which shows a very high water contact angle and superhydrophobicity. The modified surface shows excellent non-wetting and non-permeability properties (Genzer and Efimenko 2000). A PDMS-based aerosol-assisted chemical vapor deposition (AACVD) coating was achieved on copper meshes for oil/water separation, and it showed a maximum water contact angle of 167° with an oil separation efficiency >99% (Figure 13.10). Superhydrophobic-coated meshes allow the permeation of oil through the pores as water molecules get repelled from the membrane surface (Crick, Gibbins, and Parkin 2013). Yilgor et al. reported that the coating of hydrophobic silica over various substrates shows a water contact angle of about 170° ± 1°. The hydrophobic coating on various polymeric surfaces such as polystyrene, epoxy, poly(methyl methacrylate), and polycarbonate was studied (Yilgor et al. 2012). A hydrophobic patterned surface is an approach created by a simple template method that leaves a 3D micropatterned surface over the polyethylene film. This hydrophobic pattern has an excellent stability in terms of abrasion resistance, which persists even after more than 5000 abrasion cycles (Xu, Mondal, and Lyons 2011; Asthana et al. 2014).
Silica Nanoparticles:
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials II, 2021
Atul Dev, Mohammad Nadim Sardoiwala, Surajit Karmakar
CVD is a route to deposit a solid material onto a substrate via surface reaction in the gas phase. Various forms of CVD have been utilized, butmost commonly, firstly precursors are vaporized. Sonication, thermal heating, and pressure reduction are common methods to be used for vaporization (Licausi et al. 2011). In the CVD process, after vaporization, reactants are activated by using heating (Shi et al. 2011), electromagnetic radiation (Santucci et al. 2010), and plasma activation (Wang et al. 2011b). Hydrophobic material deposition with CVD is a challenging process. In general, the outcome of CVD provides a flat and chemically homogeneous deposition. So, surface roughness has been achieved by the further introduction of nanoparticles (Wang et al. 2011a). In the case of silica coating, surface chemical composition has been modified with post-treatment. Silica surface is generally hydrophilic due to the presence of hydroxyl groups on their surface that favors reaction with water molecules (Laskowski and Kitchener 1969). Lower surface energy and reduced interaction with water help to achieve hydrophobic silica. Commonly, FAS molecules are applied to obtain a superhydrophobic surface of silica (Xu et al. 2009), which is costly. Hence, new and cost-effective routes are required to deposit superhydrophobic material by using CVD.Generally, surface coating of SiO2 is performed via CVD using SiCl4. The reaction is bifurcated into two reactions as follows (Klaus et al. 1997): SiOH*+SiCl4→SiOSiCl3*+HClSiCl*+H2O→SiOH*+HCl(*indicates surface species)
Anti-fingerprint properties of engineering surfaces: a review
Published in Surface Engineering, 2018
M. Belhadjamor, M. El Mansori, S. Belghith, S. Mezlini
Huang et al [154]. have used multi-scale nano-/micro-roughness structures to construct super-hydrophobic coating (Figure 16). The presence of the hydrophobic silica nanoparticles enables the increase of the water contact angle. Moreover, the nanoscale roughness reduces adhesion forces between the water drop and the surface. This phenomena is behind the dramatically decrease of the contact angle hysteresis which is about 85% between smooth particles (Figure 16(a–c)) and particles with nanoscale roughness (Figure 16(d–i)). This effect improves the self-cleaning properties. The surface repellency against liquids with low surface tension should be evaluated to broaden its application fields (e.g. anti-fingerprint application).
Low-cost fabrication of flexible water-repellent film by spray coating of a hydrophobic nanoparticle dispersion
Published in Journal of Dispersion Science and Technology, 2020
Young-Sang Cho, Soyoung Nam, Sol Jeong, Young-Seok Kim
Commercial or synthesized silica nanoparticles were modified using a silane coupling agent to prepare hydrophobic silica nanoparticles. Typically, 2 g of dried powder was added to 40 mL of toluene under stirring and the coupling agent (1 mL) was subsequently added to the mixture. The resulting suspension was heated at 70 °C for 3 h under reflux. After the modification, the sediment was obtained by stopping stirring and careful removal of the supernatant. The resulting hydrophobic silica nanoparticles were then dried at room temperature for several days.