超亲油――超疏油

Abrifeintroductionaboutsuperoleophobicsurface何灵欣、汪聿琛、张振华来自大自然的灵感？人们受这些生物的启发，通过构筑微纳复合结构以及修饰低表面能物质，制备了一系列具有自清洁效应的超疏水表面,并在织物建筑物表面和车窗玻璃等领域得到广泛应用。但超疏油表面(对油的接触角大于150°)的制备一直是一个难题为什么理由:因为油等有机液体的表面张力远远小于水，一般在20～30mN/m相比于水的表面张力295K下水的表面张力系数为72.75mN/m解决办法目前常用的做法是在微纳粗糙结构的基础上引入含氟的低表面能物质缺陷这些含氟物质通常价格昂贵且对环境有毒有害，限制了超疏油材料发展和应用．更重要的是，这些表面只在空气中具有超疏油性质，一旦置于水下便会丧失超疏油性，变成亲油的表面需要一种水下超疏油材料theremarkableoil-repellentabilityoffishscales,whichallowsfishtosurviveinoil-pollutedwater什么是水下超疏油表面水下超疏油表面是指在油/水/固三相体系中，对油的接触角大于150°的固体表面，且滚动角小于10°鱼鳞化学组成是亲水性的羟基磷灰石蛋白质和一层薄薄的黏液在空气中，鱼体表是超亲油的，而在水下却表现出超疏油的性质，对油的接触角为(156.4±3.0)°对比其在空气中超亲油和水下超疏油的特点，我们认为对于浸润性的转变，水相起到关键的作用Fig.1SurfacestructuresoffishscalesandbiomimicPAMhydrogelsurface:(a)opticalimageofthefishscales，(b～c)SEMimagesoffishscalesatlowandhighmagnificationsand(d)PAMhydrogelfilmwithfish-scalestructures(Theinsertsareoildropletonthesurfaceunderwaterandhighmagnificationimage．)(ReproducedfromRef，withpermissionfromWiley-VCH)我们认为对于浸润性的转变，水相起到关键的作用．当油滴接触到水中的鱼体表面时，水分子陷入亲水的鱼体表面的微纳米结构中，对油滴产生排斥，形成了油/水/固的复合界面，从而形成了超疏油的性质Fig.2(a～c)SEMimagesofthesubstratesandshapesofoildropletstakenatdifferentstagesduringnormaladhesiveforcemeasurementprocessondifferentsubstrates:onthe(a)smooth，(b)microstructuredand(c)micro/nanostructuredsiliconsubstrates;Diagramsillustratingtheeffectofsurfacestructureonthewettingbehaviorsofsolidsubstratesinoil/water/solidthree-phasesystems:Aliquid1dropleton(d)smoothsurface，(e)microstructuredsurfaceand(f)micro/nanostructuredsurfaceinaliquid2phase(ReproducedfromRef．［18］，withpermissionfromWiley-VCH)微纳复合的粗糙结构Cassie方程的推广其中f是固体表面所占水/固界面的比例，Θ3是水下油滴在光滑的固体表面的接触角，Θ'3水下油滴在粗糙的固体表面的接触角总的来讲——亲水性的化学组成和微纳复合的粗糙结构是设计水下超疏油表面的关键因素Preparationandcharacterizationofasurfacewithswitchablesuperoleophilicityandsuperoleophobicityonanon-woventextilesubstrate.(a)Schematicshowingthepreparationstrategyforasurfacewithswitchablesuperoleophilicityandsuperoleophobicityonanon-woventextile.(b)Scanningelectronmicroscope(SEM)imageoftherawtextile.Inset:enlargedviewofthesurfaceofasinglefiber.(c)SEMimageofthetextileafterdepositionofsilicananoparticlesandblockcopolymergrafting.Inset:enlargedviewofthesurfaceofasinglefiber.Oilwettabilityofthefunctionalizedtextileinaqueousmedia.(a)StillimagesfromvideoCAmeasurementsofaDCEdropletonthefunctionalizedtextilesurfaceinwaterwithapHof6.5.(b)SnapshotsshowingtheabilityofthefunctionalizedtextileforthecaptureofanoildropletinaqueousmediawithapHof6.5.Ingreaterdetail,anoildropletstainedwithoilredOwasfirstdroppedtothebottomofabeakercontainingwaterwithapHof6.5.Then,apieceofthefunctionalizedtextilewasloweredintothewatertoapproachtheoildroplet.Oncontact,thetextileimmediatelysuckeduptheoildroplet,leavingbehindnooilresidue.(c)ImageofaDCEdropletappliedonthesurfaceofthetextileinwaterwithapHof2.0.(d)PhotographofDCEdropletssittingonthefunctionalizedtextileinacidicwaterwithapHof2.0.TheDECdropletswerestainedwithoilredOforclearobservation水下超疏油表面的制备方法自上而下自下而上Structuresofunderwatersuperoleophobicsurfacesfromtypicalfabricationapproaches:(a)PNIPAAmhydrogelwithmicrostagearraysfabricatedbytemplating(b)PPynanotubearraysfabricatedbyelectrochemical(c)Filmswithnanoparticlesarraysfabricatedbyself-assemblemethodd)PNIPAAmgraftedsiliconnanowirearraysfabricatedbysurface-initiatedatomtransferradicalpolymerization模板法电化学聚合法胶体粒子自组法聚合物分子刷法几个有趣的应用•表面具有水下油滴黏附状态温度响应性可控的性能•通过电化学反应调控表面的微纳米结构实现控制油滴的运动行为•具有选择性的油水分离结语——水下超疏油表面的研究进展令人兴奋和神往，不过目前理论体系需要进一步的发展和完善，不过我们相信，这些研究将会极大地造福人类。REFERENCES[1].薛众鑫,江雷.仿生水下超疏油表面[J].高分子学报,2012,10[2].卢晟,李梅.超疏油表面研究进展[J].2012,CB9338[3].LianbinZhang,ZhonghaiZhangandPengWang.Smartsurfaceswithswitchablesuperoleophilicityandsuperoleophobicityinaqueousmedia:towardcontrollableoil/waterseparation[J].NPGAsiaMaterials(2012)4Thethermal-responsiveadhesionbetweenthesurfaceofPNIPAAmhydrogelandoildroplets:(a)theoildropletcaneasilyrolloffthesurfaceat23℃，whilefirmlyadheresonthesurfaceat40℃，(b)ann-hexaneoildropletcouldspontaneouslyflyawayfromthesurfacewhendecreasingtheenvironmentaltemperaturefrom40℃to23℃，(c)adhesiveforcemeasurementsusingoildropletsasdetectingprobes(ReproducedfromRef．［26］，withpermissionfromtheRoyalSocietyofChemistry)ThesmartcontrolofanoildropletmotiononthenanostrcturedPPysurfacebyadjustingtheelectrochemicalpotentials:(a)anoildropletwasparkingonthesurfacebyadhesion，(b)thecontactangleofoildropletincreasedandadhesiondecreasedwhenthePPysurfacewasreduced，(c)theoildropletbegantorun，(d)theoildropletbrakedandadheredonthesurfaceagain，(e～g)theoildropletcamebacktothesuperoleophobicandlow-adhesionstateandrolleddown．(ReproducedfromRef．［27］，withpermissionfromAmericanChemicalSociety)