Superhydrophobic surfaces are currently a subject of great interest and enthusiastic study because of their various important applications.In this paper

the relationships between contact angle

surface roughness and surface morphology were discussed to explore a simple procedure for preparing a superhydrophobic aqueous coating with tunable roughness surface.Transparent hydrophobic films with fluorine gradient distribution have been prepared from methacrylate copolymers modified with fluoroacrylate and siloxane(γ-methacryloxypropyltriisopropoxysilane) in emulsion polymerization.The fluorine gradient distribution resulted from fluorine self-assembled was examined by X-ray photoelectron spectroscopy analysis.The strawberry-like silica particles are obtained by utilizing the graft of different size silica particles modified with epoxy and amine functional groups

respectively.This makes the film form a composite interface with irregular binary structures and a hierarchical roughness to have high air-trapped ratio.The superhydrophobic surface was obtained by making use of silica particles to increase roughness and fluorocopolymer to provide low surface energy.By comparing the difference of water contact angles on the film surfaces between the admixture of fluoroemulsion with the sole diameter silica and that with composite silica particles

it was shown that the large roughness factor is not necessary while the high air-trapped ratio is indispensable.Although the composite silica particles play a vital role in governing the surface wettability

it is necessary to combine with a low surface energy to make a surface superhydrophobic.The composite surface turns from hydrophilic to superhydrophobic only when there is a proper cooperation with the fluorocopolymer having low surface energy

and the water contact angle will decrease when the mass ratio of emulsion to silica exceeds unity because of the filling of interspace on the film surface.The largest contact angle for water on the surface of hybrid film is about(174.2±2)° and the contact angle hysteresis is close to 0°.