从超亲水到超疏水

Electro-ResponsivelyReversibleTransitionofPolythiopheneFilmsfromSuperhydrophobicitytoSuperhydrophilicity

LianyiXu,QiangYe,XueminLu,andQinghuaLu*

SchoolofChemistryandChemicalEngineering,ShanghaiJiaoTongUniversity,Shanghai200240,People’sRepublicofChina*SupportingInformation

Controlofsurfacewettabilityisofconsiderabletechnologicalampli?cationofsurfacewettabilityproperties,17,31?36theandscientiprocessesarecomplicatedandadditionalsubstancesneedto

?7?cimportance,withapplicationsinself-cleaningsurfaces,1antifoggingbe

12surfaces,8,9micro?uidsystems,10,11andbiotechnology.Surfacewettabilityisusuallygovernedbythe?added.Thismaycausea

surfacegeometryandchemicalcomposition.1,5,13Smartandlmconductiveoraweakeningreductioninthetransparencyofthesubstrate.oftheForadhesionexample,betweeninpreviousthepolymerwork,17layerFe3+surfaceswithreversiblyswitchablewettabilityhavereceivedwasincludedascatalystintheplatingsolution,andcouplingofspecialattentionduetotheirvitalimportanceinmany?elds.electropolymerizationandFe3+-catalyzedchemicalpolymer-Suchsurfacesmaybeconstructedbyintroducingastimuli-izationpromoted

responsivematerialintoanappropriatelyroughstructure,14?1927thegrowthofaporous,roughPPy?lm.Inthe

andthereversibleswitchingfeaturecanberealizedwiththe?secondstudy,thelatexassemblyofPS

helpofanexternalstimulussuchaslightirradiation,20?22technique,atconductingandthensubstratethepolythiophenewas?rstcarriednanoparticlesonaderivativeoutbywasanelectro-LB-liketemperature,18pH,23solvent,19,24orelectricalpotential.25?28depositedtoformaroughpolymersurface.TherequiredAmongstimuli-responsivematerials,π-conjugatedpolymersareroughnessofthePSnanoparticlesmayhavereducedthetypicalelectrochemical-responsivematerialsandcanbeeasilyconductivityoftheelectrochemicallydeposited?lm.Therefore,prepared.17,27,29,30Inparticular,forπ-conjugatedpolymersthatsuchelectro-activeπ-conjugatedpolythiophene?lms,whicharecanbedoped(oxidized)anddedoped(reduced)byapplyingaeasytoprepareonalargescale,haveremainedunexploredforvoltageinanelectrolytesolution,theseprocessesarewettingswitchingapplication.

accompaniedbycounterions(dopants)movingintoandoutInourearlierstudy,anelectro-responsivedouble-layerofthe?lm.Thismayresultinaconversionofthewettingpolythiophene?lmwaspreparedforwater-dropletadhesionpropertiesoftheπ-conjugatedpolymer.Yanetal.employedswitchingreversibility

per?uorooctanesulfonatetodopepolypyrrole(PPy)?lm,which37betweenslidingandpinnedsuper-hydrophobicstates.Thispreparationprocessdidnotneedresultedinachangeinsurfaceanyadditiveforthecreationofaroughsurfaceandlowsurface

17wettingfromsuperhydrophilicitytosuperhydrophobicity.Advinculaetal.electrochemicallyenergy.Poly(3,4-ethylenedioxythiophene)(PEDOT)was

polymerizedapolythiophenederivative,poly(G0?3TCOOR),directlyelectrodepositedonanindiumtinoxide(ITO)-coatedasasurfacelayeronpolystyrene(PS)nanoparticles,andfoundglasselectrodetoprovideaporousconductingsubstrate.Onthatthewettingcouldbeswitchedbydopinganddedopingoftetrabutylammoniumhexa?uorophosphate.27AlthoughhighlyReceived:July4,2014

porousstructuresofπ-conjugatedpolymer?lmswereAccepted:August12,2014

successfullyachievedinthesetwostudies,whichisnecessaryPublished:August12,2014

?2014AmericanChemicalSociety14736dx.doi.org/10.1021/am5043627|ACSAppl.Mater.Interfaces2014,6,14736?14743

Figure?lm,and1.(c)ScanninghighlyelectronporousPEDOTmicroscopy?P(3-MTH)(SEM)image?lm.of(d)theMagnielectrodeposited?edimageof?lms:PEDOT(a)?P(3-MTH)P(3-MTH)?lm,showing(b)highlythenetwork-likeporousnetwork-likenanostructure.

PEDOTthesurfaceoftheporousPEDOT,hydrophobicpoly(3-(FEI,Hillsboro,OR).Staticwatercontactanglemeasurementswerehexylthiophene)(P(3-HTH))wasfurtherelectrodeposited.performedbythesessiledropmethodonaContactAngleSystemSuchdouble-layerpolythiophenepossessesastronglysuper-OCA20(DataPhysicsInstrumentsGmbH,Germany)inair.Thehydrophobicsurfacebothatdopinganddedoping,thatis,theircontactanglesreportedhereinaremeanvaluesmeasuredfor4μLstaticwatercontactangle(WCA)isalwaysgreaterthan150°,waterdropletsat?vedi?erentpositionsoneachsample.WaterSAswhichprovidesagoodplatformforthepreparationofadhesionweredeterminedbyslowlytiltingthesamplestageuntila4μLwaterswitching(slidingangle(SA)changesbetween0°and>90°).dropstartedmoving.ThechemicalcompositionsofthesurfaceswereDeferenttotheabove-mentionedwork,inthiswork,wedeterminedbyX-rayphotoelectronspectroscopy(XPS)onaKratosfocusedonanelectro-responsivewettingswitchingreversibleAxisUltraDLDspectrometer(KratosAnalytical,Ltd.,Manchester,betweensuperhydrophobicityandsuperhydrophilicity(WCAU.K.)withamonochromatedAlKαradiationsource(1486.6eV)andchangesbetween>150°and～0°).Thereby,theoverlyingatakeo?angleof90°.UV/visspectraofthe?lmsontheITOsubstratepolythiopheneP(3-HTH)wasreplacedbyanotherpolythio-weremeasuredonaPerkinElmerLambda20UV/visspectrometer.phenewithashorteralkylgroup,poly(3-methylthiophene)Photographsandmoviesweretakenwithacamera.2.3.ElectrochemicalSynthesisandExperiments.Allelectro-(P(3-MTH)),tomoderatelytunethehydrophobicityofchemicalexperimentswereperformedinanelectrochemicalcell(1×double-layer1×4.5cm)withathree-electrodesystembyusingacomputer-??lm.Theobtaineddouble-layerpolythiophenecontrolledCHI630EElectrochemicalAnalyzer.Theworkingwithlm(PEDOTaWCA?>P(3-MTH))150°.ThroughexhibitedcontinuouslysuperhydrophobicitydopingandelectrodewasITOglass(<10Ωsq?1,0.9×5cm),whichwasdedopingatredoxpotentials,theas-preparedPEDOT?P(3-washedsuccessivelyunderultrasonicationwithdeionizedwaterandMTH)?lmdisplayedareversibleconversionbetweensuper-absoluteethanolandthendriedwithastreamofN2beforeuse.Thehydrophilicityatthedopedstateandsuperhydrophobicityatcounterelectrodewasaplatinumwire(1mmdiameter),whichwasthededopedstate.Thiswettabilityswitchinghasbeencleanedbeforeeachexamination.AnAg/AgClwirewasusedasainvestigatedbypreciselyadjustingthedopinganddedopingquasi-referenceelectrode.Allelectrochemicalexperimentswerepotentials.performedatroomtemperatureand<40%relativehumidity.

Polythiophene?lmswereelectrodepositedonITOelectrodesby

2.EXPERIMENTALSECTIONcyclicvoltammetry(CV)inACNsolutioncontaining0.2MLiClO

supportingelectrolyte.All?lmswererinsedtwicewithACN(24as

the×

2.1.Materials.Commercialhigh-performanceliquidchromatog-ca.1mL)andthendriedatroomtemperatureforseveralminutesraphyunder?owingN2beforecharacterization.

Chemicalgradeacetonitrile(ACN)wasprovidedby2.4.ElectrochemicalPreparationofP(3-MTH).AP(3-MTH)puriReagentCompanyandwasusedShanghaiwithoutLingfengfurther?

(3-MTH),?cation.substratelmwasdirectlyof0.05Melectrodeposited3-MTHelectrolytebyCVsolutionontobetweenasmooth0andITO+1.9glassVlammoniumanhydrous3,4-Ethylenedioxythiophene

oratconstantpotential(+1.9V;Q≈330.9±20mCcm?2)(Figure

purchasedhexa?uorophosphatelithiumperchlorate(EDOT),

((CH(LiClO3-methylthiophene

4),andtetrabuty-

3CH2S1,SupportingInformation).TheP(3-MTH)couldbedopedat+1.2

2.2.Characterization.fromAladdin.)4N+PF6?,TAHFP)wereField-emissionscanningelectronmicros-V(oxidation)anddedopedat0V(reduction)inACNsolutioncopy(FE-SEM)wasperformedwithaNovaNanoSEMinstrumentcontainingLiClO4asthesupporting

electrolyte.

14737dx.doi.org/10.1021/am5043627|ACSAppl.Mater.Interfaces2014,6,14736?14743

Figureresolution2.(a)XPSXPSspectraspectraofClof(2p,the(blue)207.0eV)dedopedinthePEDOT,(green)anddedopedPEDOTand?(red)P(3-MTH)dopedinPEDOTthe(green)?

P(3-MTH).

dedopedand(red)dopedstates.(b)High-Figure13.(a)CyclicvoltammogramsofPEDOT?P(3-MTH)inmonomer-free0.2MLiClO4/ACNsolutionatscanratesbetween100and300mVs?respectively.

.(b)Peakcurrentdensity(jpaandjpc)vsscanningrate;jdenotesthecurrentdensity;paandpcdenotetheoxidationpeakandthereductionpeak,2.5.ElectrochemicalPreparationofPEDOT?P(3-MTH).AnunderlyingcomprisedcontainingaporousPEDOTMEDOTelectrolyte?lmofPEDOTsolutionwasbetween?rstelectrodeposited?0.7and+1.6byV,CVapplyingofa0.01anlinkedelectrodepositionplatinumto0.2MLiClO?P(3-MTH)?lmandawaterdroplet4sittingonthe?lm.ThewaterdropletwasSupportingcharge(Q)ofabout32.5±2mCcm?2(FigureS2a,electrode.wire,thecounterMTH)potentialTheand(negative)electrodebya1mmdiameterelectro-wettingthe?lmwastestlinkedtothework(positive)CVofa?0.05lmInformation).wasM3-MTHelectrodepositedThereafter,solutionbetweenontheapoly(3-methylthiophene)as-preparedP(3-?0.4and+1.9PEDOTV,with?lmQby≈MTH)64.2wasrecorded?lm.of+1.5TheVusingwaterbetweenaContactdropletthewaterwasdropletdoneandusingthePEDOTatransition?P(3-AnglechangeSysteminWCAOCAwith20.