Generation of superhydrophobic surfaces by electrospinning process

A surface having water contact angle (WCA) higher than 150o is named as superhydrophobic surface. To exhibit superhydrophobic feature, a surface should have micron scale roughness on an inherently hydrophobic material. This extreme water-repellency feature has found many applications both in industry and in daily-life. Current production processes of superhydrophobic surfaces are either time consuming or expensive. A cost-effective, widely applicable and practical way of production is necessary. In this study, superhydrophobic surfaces were generated by utilization of electrospinning process, which is a continuous nanofiber production process from a polymeric solution under an electrical field. By this method, a straightforward and inexpensive way to fabricate very stable superhydrophobic surfaces with an advantage of tunable WCA and low sliding angle were discovered. Poly-(acrylonitrile-co-dimethyl meta-isopropenyl benzyl isocyanate) polymer was synthesized, and electrospun after the addition of a fluorinated hydroxyl-ended oligomer. The effects of viscosity of electrospinning solution, fluorine content and molecular weight of the copolymer to surface morphology and WCA of the electrospun film were investigated by using scanning electron microscope, goniometer, atomic force microscope and nuclear magnetic resonance instruments. Experiments proved that deliberate incorporation of the beads into the film resulted in extreme water-repellency. It was found that, as the viscosity of the solution was decreased, the density of the polymeric beads, so the film roughness in three dimensions, was increased to more than 150o WCA values for the electrospun films. In the molecular weight of copolymer study, electrospinning of lower molecular weight copolymer was generated solely bead morphology, which resulted the highest WCA of 166.7±2.2o with the lowest water sliding angle of 4.3±0.8o. In addition to these studies, the films were subjected to droplet pressing between identical superhydrophobic surfaces to determine the stability of their superhydrophobicity. And this study showed that our electrospun films have the most stable superhydrophobic state in the literature.