Fabrication Of Photo-reversible Superhydrophobic Surfaces With Switchable Sticky-rolling State Of Water Droplets

In recent years, superhydrophobic surfaces, with a water contact angle (CA)greater than150°, have received much attention not only for their significance tofundamental research but also for their important applications in fields ranging fromself-cleaning materials to microfluidic devices. Smart stimuli-responsivesuperhydrophobic surfaces with dynamically tunable wettability have recentlyaroused great interest. However, there are few reports on superhydrophobic surfacewith reversible sticky-rolling switch of water dropletsIn this paper, the fluorinated azobenzene homopolymer was synthesized by usingof4-(trifluormethoxy)aniline via diazotization, dehydration condensation andorganotellurium mediated controlled radical polymerization (TERP). Then, a surfacewith hierarchical micro-nanostructures was prepared via two-phase self-assemble.The homopolymer of fluorinated azobenzene methacrylate had a well-definesynthesized via TERP; Micro-nanostructures of surfaces had a great influence on thewettability of solid surfaces. Meanwhile, the wettability of solid surfaces and themobility of waters could be changed when the as-prepared surface was exposed underUV (365nm) and Vis (425nm).Synthesis of the fluorinated azobenzene homopolymer: TERP was a facilesynthetic technology for the fluorinated azobenzene homopolymer. And it had a welldefine since the narrow polydispersity index (Mw/Mn=1.09) of the homopolymer.The influence of wettability for the illumination of UV-Vis: The as-preparedsurface consisted of an array of hierarchical macro-nanostructured particulates withmany nanofolds on the surface before UV (365nm) illumination. And the watercontact angles (CAs) was147.6±2.5°. However, the nanostructures of particlesdisappeared and the particles tended to be glossy. Meanwhile, that CAs graduallydecreased as the time of UV irradiation increased. The wettability could be changedreversibly between superhydrophobic and hydrophobic when the as-prepared surfacewas exposed under recurrent UV-Vis illumination.The influence of water mobility for the illumination of UV-Vis: The waterdroplets could roll off the as-prepared surface given a small tilt angle (ca.14°) whichwas in the low-adhesive Cassie state before UV (365nm) illumination. However,water droplets could not roll off even when the substrate was turned vertically or upside down since the Wenzel state was formed between waters and as-preparedsurface after UV (365nm) illumination. Cassie-Wenzel transition of as-preparedsurface could periodically occur and the switchable mobility of water dropletsbetween rolling-off and sticky states was easily achieved via UV-Vis irradiation.