Electrospinning of a functional perfluorinated block copolymer as a powerful route for imparting superhydrophobicity and corrosion resistance to aluminum substrates

Superhydrophobic aluminum surfaces with excellent corrosion resistance were successfully prepared by electrospinning of a novel fluorinated diblock copolymer solution. Micro- and nanostructuration of the diblock copolymer coating was obtained by electrospinning which proved to be an easy and cheap electrospinning technology to fabricate superhydrophobic coating. The diblock copolymer is made of poly(heptadecafluorodecylacrylate-co-acrylic acid) (PFDA-co-AA) random copolymer as the first block and polyacrylonitrile (PAN) as the second one. The fluorinated block promotes hydrophobicity to the surface by reducing the surface tension, while its carboxylic acid functions anchor the polymer film onto the aluminum surface after annealing at 130 °C. The PAN block of this copolymer insures the stability of the structuration of the surface during annealing, thanks to the infusible character of PAN. It is also demonstrated that the so-formed superhydrophobic coating shows good adhesion to aluminum surfaces, resulting in excellent corrosion resistance.     

Enhanced superhydrophobicity of electrospun carbon nanofiber membranes by hydrothermal growth of ZnO nanorods for oil–water separation

Development of electrospun nanofiber membranes with the selective wettability characteristics for effectively separating oil–water mixtures is an extremely advisable strategy. In this study, a superhydrophobic electrospinning carbon nanofiber (F/ZnO/CNF) membrane was successfully prepared by electrospinning and in-situ growth of ZnO, and subsequent fluorination reaction with 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (POTS). Benefiting from the influence of needle-like nanostructure and low surface energy, the as-prepared F/ZnO/CNF membrane shows excellent superhydrophobicity. When the growth duration of ZnO is 3 h, the obtained F/ZnO/CNF-3 membrane possesses outstanding water contact angle (WCA, 159.7°) and splendid oil–water separation efficiency (>99 %). Meanwhile, due to its the superior environmental stability the obtained F/ZnO/CNF-3 membrane exhibits excellent low and high temperature resistance, and enhanced resistance to various organic solvents in the face of a series of harsh environments.     

Stable superhydrophobic polybenzoxazine surfaces over a wide pH range

In this study, we report on a simple two-step casting process designed to create a stable superhydrophobic surface. This method possesses the advantages of being both simple and inexpensive as well as utilizing non-fluorine-containing compounds. Most interestingly, we found that the as-prepared surface possesses superhydrophobic properties not only for pure water but also for corrosive water under both acidic and basic conditions. Furthermore, the superhydrophobic polybenzoxazine surfaces had excellent environmental stability with regard to both heating and organic solvent treatment in terms of the contact angle to water.     

ELECTROSPRAYING/ELECTROSPINNING OF POLY(y-STEARYL-L-GLUTAMATE):FORMATION OF SURFACES WITH SUPERHYDROPHOBICITY

Electrospraying/electrospinning of poly(y-stearyl-L-glutamate) (PSLG) was investigated on a series solutions with different concentrations in chloroform.Field emission scanning electron microscopy (FESEM) and attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR/ATR) were used to characterize the morphology and structure of the electrosprayed/electrospun polypeptide mats.It was found that electrospraying of PSLG with concentrations lower than 16 wt% afforded beads,while microfibers could be electrospun at the concentration of 22 wt%.The hydrophobieity of the electrosprayed/electrospun PSLG mats was investigated with static water contact angle (WCA) and tilt angle measurements.It was demonstrated that the superhydrophobic surfaces of PSLG with WCAs and tilt angles in the ranges of 150°-170°and16.5°-4.2°,respectively,were obtained through electrospraying/electrospinning process.     

超疏水低粘着铜表面制备及其防覆冰性能

用喷砂处理在铜片表面形成微米级丘陵状凹坑,再用表面氧化处理在铜片表面制备菊花花瓣状CuO纳米片.通过喷砂-表面氧化处理在铜片表面成功构建了微米-纳米复合结构,这种表面氟化后与水滴的接触角高达161°,滚动角低至1°,显示出优异的超疏水性和很低的粘着性.低温下,这种表面与水滴间的热量交换较小,水滴不易凝结,有效地提高了抗结霜性.抗结霜性良好的超疏水铜有望在热交换器或低温运行设备等领域获得应用,这种简便的超疏水铜表面的制备方法也给其它工程材料超疏水表面的工业化制备提供了一个思路.     

Fabrication of superhydrophobic polymer films with hierarchical silver microbowl array structures

Flexible superhydrophobic polyvinyl alcohol (PVA) films with silver bowl-like array structure are fabricated based on the thermal evaporation with sphere monolayer as templates and the modification of 1H, 1H, 2H, 2H-perfluorodecanethiol on silver surface. The silver microbowl arrays were composed of silver nanoparticles with an average diameter size of ca. 10 nm. The polymer films exhibit excellent stability and remarkable superhydrophobicity with a high water contact angle (CA) of about 163° and a low sliding angle (SA) of less than 3°.     

Synthetic control of cage/network ratio of poly(methylsilsesquioxane)s for storage stability,hardness, and weather resistance of coating films

Poly(methylsilsesquioxane) (PMSQ) was synthesized using a two‐step process consisting of hydrolysis of methyl trimethoxysilane (MTMS) with aluminum chelate catalyst and successive condensation reactions conducted at elevated temperatures. Results of nuclear magnetic resonance and Fourier transform infrared measurements show that all terminal functional groups were Si? OH in PMSQ. Results show further that PMSQ has both a cage structure and a network structure, and a cage/network ratio is represented by a height ratio of ?64.5/?66.6 ppm. PMSQ of different molecular weight but the same Si? OH concentration is obtainable by varying the condensation reaction conditions such as the concentration, temperature, amount of aluminum chelate catalyst, and the solvent solubility parameter. A difference of the cage/network ratio occurs. A different cage/network ratio is dependent on the different reactivities of the intramolecular and intermolecular reactions. The relations of molecular structure of the obtained PMSQ molecular structure were characterized along with functions of storage stability, film hardness, and weather resistance. PMSQ designed with a larger cage/network ratio is necessary to obtain PMSQ with good storage stability and a coating film having good weather resistance. PMSQ designed with a smaller cage/network ratio should be prepared to obtain a coating film with high hardness. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

UV and thermally stable superhydrophobic coatings from sol-gel processing

A method for the preparation of inorganic superhydrophobic silica coatings using sol-gel processing with tetramethoxysilane and isobutyltrimethoxysilane as precursors is described. Incorporation of isobutyltrimethoxysilane into silica layers resulted in the existence of hydrophobic isobutyl surface groups, thereby generating surface hydrophobicity. When combined with the surface roughness that resulted from sol-gel processing, a superhydrophobic surface was achieved. This surface showed improved UV and thermal stability compared to superhydrophobic surfaces generated from polybutadiene by plasma etching. Under prolonged UV tests (ASTM D 4329), these surfaces gradually lost superhydrophobic character. However, when the as-prepared superhydrophobic surface was treated at 500 degrees C to remove the organic moieties and covered with a fluoroalkyl layer by a perfluorooctylsilane treatment, the surface regained superhydrophobicity. The UV and thermal stability of these surfaces was maintained upon exposure to temperatures up to 400 degrees C and UV testing times of 5500 h. Contact angles remained >160 degrees with contact angle hysteresis approximately 2 degrees.     

Superamphiphilic Janus fabric

Janus fabrics with superamphiphilicity were fabricated via electrospinning of polyacrylonitrile (PAN). PAN nanofibrous mats were formed on an aluminum foil substrate and then thermally treated to cause hydrolysis. An identical PAN solution was subsequently electrospun onto the hydrolyzed PAN layer, followed by peeling off of the bicomposite film from the collector substrate to produce a free-standing Janus fabric. On one side, the electrospun PAN mat exhibited superhydrophobic properties, with a water contact angle of 151.2°, whereas the initially superhydrophobic PAN sheet on the opposite side of the fabric was converted to a superhydrophilic surface (water contact angle of 0°) through hydrolysis of the surface functional groups induced by the thermal treatment. The resulting Janus fabrics exhibited both superhydrophobicity, repelling water on the one side, and superhydrophilicity, absorbing water on the other side. The organic solvent resistance of the PAN nanofibrous sheets was remarkably improved by incorporation of a tetraethyl orthosilicate. This facile and simple technique introduces a new route for the design and development of functional smart, robust fabrics from an inexpensive, commercially available polymer.     

Fabrication of superhydrophobic polymethylsilsesquioxane nanostructures on cotton textiles by a solution-immersion process

Superhydrophobic cotton textiles are prepared by a simple, one-step and inexpensive phase separation method under ambient conditions by which a layer of polymethylsilsesquioxane (PMSQ) nanostructures is covered onto the cellulose fibers. By changing the silane precursor concentration, PMSQ nanostructures with various shapes, morphologies and sizes were fabricated. Nanostructures were characterized using SEM, EDS, and attenuated total reflectance FTIR. The wettability of the modified cellulose surfaces was characterized with contact-angle goniometry and sliding angle technique, respectively. The water contact angle of modified cotton is measured to be higher than 150°, which is high enough to exhibit the lotus effect as a result of the superhydrophobicity. Tunable water-repellent properties of the fabric are also demonstrated, with sliding contact angles varying from "sticky" to "slippery" depending upon different nanostructures on the surface of the fibers. It is expected that this simple technique will accelerate the large-scale production of superhydrophobic cellulosic materials with new industrial applications.     

Literature review on superhydrophobic self‐cleaning surfaces produced by electrospinning

Self‐cleaning surface is potentially a very useful addition for many commercial products due to economic, aesthetic, and environmental reasons. Super‐hydrophobic self‐cleaning, also called Lotus effect, utilizes right combination of surface chemistry and roughness to force water droplets to form high contact angle on a surface, easily roll off a surface and pick up dirt particles on its way. Electrospinning is a promising technique for creation of superhydrophobic self‐cleaning surfaces owing to a wide set of parameters that allow effectively controlling roughness of resulted webs. This article gives a brief introduction to the theory of super‐hydrophobic self‐cleaning and basic principles of the electrospinning process and reviews the scientific literature where electrospinning was used to create superhydrophobic surfaces. The article reviewed are categorized into several groups and their results are compared in terms of superhydrophobic properties. Several issues with current state of the art and highlights of important areas for future research are discussed in the conclusion. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Green Approach to the Fabrication of Superhydrophobic Mesh Surface for Oil/Water Separation

We report a simple and environment friendly method to fabricate superhydrophobic metallic mesh surfaces for oil/water separation. The obtained mesh surface exhibits superhydrophobicity and superoleophilicity after it was dried in an oven at 200 °C for 10 min. A rough silver layer is formed on the mesh surface after immersion, and the spontaneous adsorption of airborne carbon contaminants on the silver surface lower the surface free energy of the mesh. No low‐surface‐energy reagents and/or volatile organic solvents are used. In addition, we demonstrate that by using the mesh box, oils can be separated and collected from the surface of water repeatedly, and that high separation efficiencies of larger than 92 % are retained for various oils. Moreover, the superhydrophobic mesh also possesses excellent corrosion resistance and thermal stability. Hence, these superhydrophobic meshes might be good candidates for the practical separation of oil from the surface of water.     

Facile Electrochemical Method for the Fabrication of Stable Corrosion-Resistant Superhydrophobic Surfaces on Zr-Based Bulk Metallic Glasses

Both surface microstructure and low surface energy modification play a vital role in the preparation of superhydrophobic surfaces. In this study, a safe and simple electrochemical method was developed to fabricate superhydrophobic surfaces of Zr-based metallic glasses with high corrosion resistance. First, micro–nano composite structures were generated on the surface of Zr-based metallic glasses by electrochemical etching in NaCl solution. Next, stearic acid was used to decrease surface energy. The effects of electrochemical etching time on surface morphology and wettability were also investigated through scanning electron microscopy and contact angle measurements. Furthermore, the influence of micro–nano composite structures and roughness on the wettability of Zr-based metallic glasses was analysed on the basis of the Cassie–Baxter model. The water contact angle of the surface was 154.3° ± 2.2°, and the sliding angle was <5°, indicating good superhydrophobicity. Moreover, the potentiodynamic polarisation test and electrochemical impedance spectroscopy suggested excellent corrosion resistance performance, and the inhibition efficiency of the superhydrophobic surface reached 99.6%. Finally, the prepared superhydrophobic surface revealed excellent temperature-resistant and self-cleaning properties.     

Influence of n-hexanol and n-octanol on wetting properties and air entrapment at superhydrophobic surfaces

Superhydrophobic surfaces have recently attracted a lot of attention due to their self-cleaning properties. The superhydrophobic surfaces used in our studies were prepared using a mixed inorganic-organic coating. In order to check how short chain surface active agents affect the surface energy of such surfaces, their wettability (sessile drop technique) and the kinetics of the three phase contact formation were studied. It was found that with increasing concentrations of n-hexanol and n-octanol the surface energy of these surfaces was only slightly changed, i.e. a small decrease in contact angle values with increasing solution concentration was detected. Even for the most concentrated n-hexanol and n-octanol solutions, the contact angles were in the range 145-155° and the drop rolled off, indicating that the studied surfaces stayed superhydrophobic. Air bubbles, upon collision with such superhydrophobic surfaces, spread over the superhydrophobic surface within milliseconds in the studied solutions.     

Study of superhydrophobic electrospun nanocomposite fibers for energy systems

Polystyrene (PS) and polyvinyl chloride (PVC) fibers incorporated into TiO(2) nanoparticles and graphene nanoflakes were fabricated by an electrospinning technique, and then the surface morphology and superhydrophobicity of these electrospun nanocomposite fibers were investigated. Results indicated that the water contact angle of the nanocomposite fiber surfaces increases to 178° on the basis of the fiber diameter, material type, nanoscale inclusion, heat treatment, and surface porosity/roughness. This is a result of the formation of the Cassie-Baxter state in the fibers via the nanoparticle decoration, bead formation, and surface energy of the nanofiber surface. Consequently, these superhydrophobic nanocomposite fibers can be utilized in designing photoelectrodes of dye-sensitized solar cells (DSSCs) as self-cleaning and anti-icing materials for the long-term efficiency of the cells.     

Preparation of superhydrophobic paper mulch and study on its anti-UV performance

In order to improve the shortcomings of paper mulch, such as the low water resistance and weather fastness in practical application, the paper mulch with a superhydrophobic structure was prepared by depositing zinc oxide layer and silicon dioxide layer on the surface of paper mulch by the solution impregnation method, the paper mulch surface treatment method is simple and environmentally friendly. The surface chemical composition and surface morphology of paper mulch before and after UV aging were characterized, respectively. The wetting property, bouncing property, and mechanical stability of paper-based film were studied. The results showed that the static contact angle of the superhydrophobic paper mulch was as high as 161.77°, and the average sliding angle was only 3.5°, which also showed excellent droplet bounce performance and mechanical stability. After UV aging experiment, the static contact angle of super-hydrophobic paper mulch was increased to 163.64°, and the sliding angle was reduced to 2.5°. Its excellent performance could still be maintained, showing excellent UV resistance, which improved the weather fastness and water resistance of paper mulch to a certain extent, and laid a foundation for the next large-scale field test.     

聚苯硫醚超疏水复合涂层的制备与性能

利用工业原料聚苯硫醚微粉和疏水性二氧化硅纳米粉末,采用喷涂法在瓷砖表面制备了疏水复合涂层.研究了热处理温度、组分配比对涂层表面形貌、粗糙度和接触角的影响,发现随着热处理温度升高,涂层表面粗糙度增大,随着疏水性二氧化硅含量的增加,由于表面聚集的疏水性二氧化硅增多,涂层疏水性增强,在热处理温度为280℃、疏水性二氧化硅与聚苯硫醚质量比为1∶1时,可获得超疏水涂层,涂层的接触角大于150°,滚落角小于4°,pH值为1～14的水溶液在其表面都具有很高的接触角.超疏水涂层具有良好的自清洁效果,并且经落沙法实验测定,超疏水涂层耐刮伤性能良好.     

用于油/水分离的环保无氟超疏水织物的制备与性能

针对目前用于油/水分离的超疏水材料普遍存在的原料不环保、不可降解、涂层耐久性差等缺点,采用简便的浸渍法,制备了一种环保、工艺简单且性能优良的超疏水材料。首先,使用水性聚氨酯（WPU）将聚甲基丙烯酸甲酯-甲基丙烯酸缩水甘油酯P（MMA-r-GMA）微球固定在棉织物表面,构造微纳米级粗糙结构。其次,通过水解-缩合反应,将无毒的十六烷基三甲氧基硅烷（HDTMS）与甲基三乙氧基硅烷（MTES）锚定在棉织物表面,制备得到超疏水棉织物。结果表明,改性棉织物接触角最高可达157.3（°）,滚动角为5（°）。同时具有很好的耐溶剂性,在酸碱溶液中浸泡30 min后,接触角几乎无变化。油水分离效率最高可达97.8%,即使在经过10次循环分离之后,油水分离效率仍然在95%以上。该超疏水织物具有出色的油水分离效率和优良的稳定性,可用于可持续且环保的油水分离领域。     

Superhydrophobic polyimide films with a hierarchical topography: combined replica molding and layer-by-layer assembly

Artificial superhydrophobic surfaces with a hierarchical topography were fabricated by using layer-by-layer assembly of polyelectrolytes and silica nanoparticles on microsphere-patterned polyimide precursor substrates followed with thermal and fluoroalkylsilane treatment. In this special hierarchical topography, micrometer-scale structures were provided by replica molding of polyamic acid using two-dimensional arrays of polystyrene latex spheres as templates, and nanosized silica particles were then assembled on these microspheres to construct finer structures at the nanoscale. Heat treatment was conducted to induce chemical cross-linking between polyelectrolytes and simultaneously convert polyamic acid to polyimide. After surface modification with fluoroalkylsilane, the as-prepared highly hydrophilic surface was endowed with superhydrophobicity due to the bioinspired combination of low surface energy materials and hierarchical surface structures. A superhydrophobic surface with a static water contact angle of 160 degrees and sliding angle of less than 10 degrees was obtained. Notably, the polyimide microspheres were integrated with the substrate and were mechanically stable. In addition, the chemical and mechanical stability of the polyelectrolyte/silica nanoparticle multilayers could be increased by heat-induced cross-linking between polyelectrolytes to form nylon-like films, as well as the formation of interfacial chemical bonds.     

The role of organoclay on the properties of Polymethylsilsesquioxane: A systematic study

In this study, an attempt is made to improve the properties of PMSQ, an organosilicone polymer which possesses distinguished properties, through an easy and facile route by the inclusion of organically modified montmorillonite clay. PMSQ-clay composites were prepared by solution blending of the components initially and then heat curing under load. The effect of clay content, varied at 5–40 wt.%, on mechanical, thermal and dynamic mechanical properties was evaluated and the optimum was obtained for 20%. Morphology investigation as well as microstructure analysis revealed intercalated to exfoliated morphology of PMSQ-clay composite. An appreciable improvement in mechanical properties of PMSQ, compressive strength and impact strength in particular, was achieved by clay inclusion up to 20%. The properties declined at ≥ 30% clay loading. The composites showed increased thermal stability compared to unmodified PMSQ up to 400 °C. Also, increase in clay content accelerated conversion to ceramic SiOC. PMSQ-clay composites exhibited good visco-elastic characteristics with higher T_g probably due to enhanced polymer-clay interactions. Thus, a simple and viable method to enhance the mechanical and thermal characteristics of PMSQ by way of preparing its composite with the reinforcing filler organoclay is demonstrated here.