Tunable, Superhydrophobically Stable Polymeric Surfaces by Electrospinning

Abstract

The high water repellence of superhydrophobic surfaces is attributed to the limited contact area between the solid and water which is manifested by a high static water contact angle (WCA) and a low sliding angle. The solid-liquid interfacial energy can be minimized by engineering not only the chemistry but also the topography of the solid surface. [1,2] For example, epicuticular wax on the lotus leaf is an intrinsically hydrophobic material.[3] However, when nano-sized crystals of wax cover a micron-level rough surface, as is the case on the lotus leaf, the WCA is further enhanced to 1608, which is defined as superhydrophobic. [4][5][6][7][8] In this case, the water droplet forms a three-dimensional, discontinuous, triphasic (water-air-solid) contact line [9] that is relatively longer and less stable than such a line on a macroscopically smooth surface. Moreover, a nonhydrophobic material can also be rendered hydrophobic with a WCA well above 1508 by chemical modification, for example, through the incorporation of fluorine or silicone, as well as by increasing the roughness. [9][10][11][12][13][14] Such an extreme water repellence is highly attractive for novel industrial and practical applications: continuously clean buildings, windows, and outdoor decorations, stain-resistant fabrics, antifouling marine structures, and oxidation-resistant surfaces. [2,8,10] Currently, the production of superhydrophobic surfaces is based on time-consuming, expensive, and/or nonversatile processes, such as controlled crystallization, lithography, etching, and templating. [9][10][11][12][13]15] To mimic the topography of the lotus leaf and to achieve a high WCA, we fabricated a polymeric film surface with a high degree of roughness through a simple and practical electrospinning process.[16] Electrospun films consist of a continuous, nonwoven web of fibers (with diameters in the order of 1-1000 nm) and, depending on processing conditions, with polymer droplets either as isolated spheres (> 1 mm in diameter) or strung along a fiber. [17][18][19][20][21][22] The electrospun film is produced by applying an electrical bias from the tip of a polymer solution-filled syringe to a grounded collection plate. Along the trajectory of the extruded polymer fiber, most of the solvent evaporates, such that a mat of randomly aligned fibers collects and form a thin film. In addition to surface roughness, the film properties were optimized by chemical modification, such as the addition of fluorine to enhance and stabilize WCA values and the incorporation of crosslinking for solvent resistance. Our ability to engineer both the physical and chemical properties of the electrospun films enables flexibility in tuning the degree of hydrophobicity.A thermoset polymer was synthesized by first reacting acrylonitrile (AN) and a,a-dimethyl meta-isopropenylbenzyl isocyanate (TMI) in N,N-dimethylformamide (DMF), and then mixing the resultant poly(AN-co-TMI) with a perfluorinated linear diol (fluorolink-D) and tin(ii) ethyl hexanoate (T2EH) in DMF. The solution w...

New Electrospun Polystyrene/Al2O3 Nanocomposite Superhydrophobic Coatings; Synthesis, Characterization, and Application

“…However, when the size of SiO 2 nanoparticles was increased to 150 nm, the WCA was decreased drastically to 124 • . On the other hand, Karapanagiotis et al [52] used Al 2 O 3 nanoparticles with different sizes (25,35, and 150 nm) in their coatings, and they found that the coating wettability is independent of the size of the nanoparticles. Then, in a more recent study, they [53] found an effect for the size of the nanoparticles on the wettability of their coatings, only if the concentration of the nanoparticle is high.…”

Preparation and Characterization of Polyvinylidene Fluoride/Graphene Superhydrophobic Fibrous Films

“…In addition to the above, electrospinning is also a predominant and promising technique to develop superhydrophobic surfaces from some polymers with low surface energies and introducing the hierarchical structure to them. In recent years, several types of superhydrophobic surfaces, produced by electrospinning of PVDF, have been reported in the literature [21][22][23][24][25][26]. Additionally, it will be a good task to obtain a kind of novel film with PVDF/graphene electrospun thin layers coated on the surface of porous supports like polypropylene (PP) and polytetrafluoroethylene (PTFE).…”

Tunable, Superhydrophobically Stable Polymeric Surfaces by Electrospinning

“…[9][10][11][12][13]15] To mimic the topography of the lotus leaf and to achieve a high WCA, we fabricated a polymeric film surface with a high degree of roughness through a simple and practical electrospinning process. [16] Electrospun films consist of a continuous, nonwoven web of fibers (with diameters in the order of 1-1000 nm) and, depending on processing conditions, with polymer droplets either as isolated spheres (> 1 mm in diameter) or strung along a fiber. [17][18][19][20][21][22] The electrospun film is produced by applying an electrical bias from the tip of a polymer solution-filled syringe to a grounded collection plate.…”