Research On Wettability Of Material Surfaces And Fabrication Of Underwater Superoleophobic Surfaces With PH Responsive Properties

Wettability of a solid surface is important and governed by both the chemical composition and the geometric structure. It has been applied in various fields such as lubricating and friction of machines, self-cleaning and anti-corrosion coatings. Therefore, it has attracted increasing attention recently.Herein, the effects of surface free energy, surface tensionand roughness on the wetting state of materials was studied. Moreover, the influence of the fraction of polar force and dispersion force of surface tension was also analyzed. It is showed that the surface energy and surface tension could significantly affect the wettability of solid surfaces. Meanwhile, the fraction of dispersion force and polar force of surface energy and surface tension also affect the wettability of a surface. Wettability can be changed by constructing specific microstructure on material surfaces, and our results provides a theoretical basis for preparing superhydrophobic surface with hydrophilic materials. In addition, it is illustrated that the underwater wettability of a surface can be deducted in terms of the solid surface energy and liquid surface tension.Large quantity positive charges on the main chain of chitosan were employed in this work to self-assemble through ionic interaction with negatively-charged functional units, and nanoparticles with charges were be prepared. Films containing chitosan nanoparticles were prepared using Layer-by Layer self-assembly method. The self-assembled films are hydrophilic and oleophilic in air, but shows underwater oleophobic propertiesresponsive to pH of the surrounding solution. When the pH of the surrounding aqueous solution is greater than 8, the film shows underwater superoleophobic property. The underwater superoleophobic property of the films can be recovered and is very stable. SEM and AFM images show that the surface roughness of the films greatly increase with the increasing of the pH value the surrounding solution, and may result in the pH responsive wetting ability.