The Synthesis And Application Of Superhydrophobic Smart Surface

Wettability is an important parameter to mesure solid surface property,which affects people's daily life.One of the base parameters of surface wettability is contact angle,when water contact angle for a surface is greater than 150°,the surface is called superhydrophobic surface.Inspired by lotus effect,superhydrophobic surfaces have drawed increasing attentionas from researchers because their wide application prospects.Furthermore,when the surfaces are sensitive to the external stimuli such as elctrocity,temperature,pH,light and so on,the wettability of smart surface can be dynamically controlled.Photoactive superhydrophobic surfaces possessing dynamically controlled wettability have recently aroused great interest because of their potential industry applications in oil water separator,self cleaning,photoconverter,intelligent membranes,etc.People have fabricated a series of photo-reversible superhydrophobic surface combining photoactive molecular or polymers in recent years,after being inspired from natural plants and animals with special wetting behaviors.However,amony various kinds of photoactive materials,therearefewreportsoncoumarinedphotoresponsivesurfacewith superhydrophobicity.Moreover,a surface with special structures oringinates from the sunny surface of paper mulberry leaf by bionic method,and on this basis a staments-like surface with wettability controlled is fabricated by a novel reverse method,as we have seen,which has not reported.To overcome the above problems,the photoactive small molecular of coumarin and spiropyran are combined with inorganic nonoparticles and nonvelent polymers,respectively,a series of new surface with wettability controlled and morphologies controlled is synthesized by common grafting method and the combined method of bionic method and reverse method.Details are as follows:1.Firstly,6-chloro-1-hexanol is introduced into 7-hydroxycoumarin molecule to synthesize the long chain 7-?6-hydroxy hexyloxy?coumarin.Secondly,the long chain coumarin modifies fumed SiO₂-TDI?CMFST?nanoparticles.Finally,a stable superhydrophobic surface with photoresponse was fabricated successfully.The morphological changes of CMFST particles are examined by scanning electron microscopy and further verified by atomic force microscope.The CMFST particles form necklaces due to the formation of the dimers of coumarins,when the CMFST particles supesion is irradiated by 365 nm UV lighunpon,which results that the CA switchs regularly.Whereas,the necklace nanoparticles recover to random nanoparticle aggregates with the cleavage of dimers under UV irradiation at 254 nm and the CA is restored to its initial value.The results indicate that the surface wettability can be transformed between hydrophobicity to superhydrophobicity reversibly.Through the study of the mechanism of surface wettability:the transition between Wenzel and Cassie can well explain the switch of surface wettability between hydrophobic and superhydrophobic.2.Mutually duplicated templates of paper mulberry leaf are fabricated successfully,and they not only have special structures and exhibit novel versatile applications.Not only dust particles but also SiO₂ particles in suspension can be collected in inverse conical holes directionally of the template.Furthermore,a superhydrophobic stamens-like surface is synthesized only by a novel reversal process based on the property of directional particle collection.In addition,the wettability of the stamens-like surface ranges from hydrophobicity to superhydrophobicity,which is controlled by regulating the content of the hydrophobic particles.On the other hand,the other template possesses performance of effective collecting fog for its conical-like structures.Finally,a complete circulation is formed consisting of the two mutually duplicated templates and specific application examples for their functions,particularly the surface with directional collecting particles and the novel stamens-like surface,which benefits the recycle utilization of material resources and environmental protection.3.An interesting morphological control of the microstructures of photoactive spiropyrans.These microstructures exhibit reversible photoisomerization in solid state under different light irradiation.To observe morphological changes intuitively caused by volume expansion of spiropyrans,a special film is synthesized with inverse conical-hole structures by biomimetic method.When a drop of spiropyran-silica mixture ethanol suspension is placed on the film and dried naturally,almost all spiropyran-silica mixture particles gather into inverse conical holes of the film.Then mixture particles in holes start distributing on edge areas of the inverse conical holes on the negative template upon 365 nm light,and disperse evenly on the entire surface of the template,and,eventually,convert into self-assembled plate structures.In addition,particle state can recover to its original state,when irradiate with visible light.4.A photoresponsive spiroyraned negative template of mulberry leaf is fabricated,researching the switching of surface wettability under light irradiation and the photochromic property of the surface,and makeing a primary research on acidic sensitivity of the surface.The paper mulberry leaf and taro leaf are choosed as comparison objiects for their different structures and wettability,and spiropyran is choosed as used photoactive molecular,then the effect of photoresponse wettability affected by rough surface is investigated.