从超亲水到超疏水(2)

timeprolonginglow-adhesion±5mCelectrodepositionsuperhydrophobiccm?2(FigureS2b,SupportingInformation).Notably,achargeused?lmtocouldapplyonlythebesurfaceobtainedP(3-MTH)whenthemoieties3.RESULTSANDDISCUSSION

moieties.wasnearlytwicethatusedforthe3.1.MorphologyandChemicalCompositionof+1.2PEDOT?P(3-MTH).Ingeneral,electrodepositedpolythio-MTH)VforThe5s)constant-potentialanddedoping(atmethod?0.2Vwasfor10appliedunderlyings)fordopingPEDOT(at2.6.inofPEDOT?P(3-Electrochemicalmonomer-freeelectrolyteCharacterizationsolutions.

oftheFilms.Thepheneswithshortalkylsidechains(typicallyn≤6inelectrochemicalpropertiesoftheas-preparedPEDOT?P(3-MTH)inCnH2n+1groups)donotprovidesu?cientroughnesstosupportelectrolyteasuperhydrophobic/superhydrophilicconductingsurface.37?39toForexample,thesurfacetopographyofelectrodepositedP(3-voltammograms+1.2Vsolutionatscanwereratescharacterizedbetween100bysweepingand300potentialsmVs?1of?0.4MTH)isshowninFigure1a.ThisP(3-MTH)?lmdisplayedandP(3-MTH)?oflmstheinas-preparedelectrolytesolutionPEDOTwere?P(3-MTH),obtainedatPEDOT,.Cyclicascanonlyrate±LiClO5°a)wettabilitytochangefromhydrophobicity(WCAof115.2°athydrophilicityanappropriate(35.5oxidation°±5°)potentialafterdoping(FigureitwithTAHFP/ACN2.7.of200ElectrochemicalmVs?1.

Solution.ThePropertiesCVcurveofofPEDOTPEDOT?P(3-MTH)?P(3-MTH)Film?lmin4S3,SupportingInformation).However,anelectrodepositedina0.2MTAHFP/ACNsolutionwascreatedbyscanningthepotentialfrom?0.4to+1.6to?0.4Vwithascanrateof200mVs?1PEDOT?lmhasahighlyporousnetwork-likestructureInthiselectrolytesystem,PEDOT.(electrodepositioncharge(Q)=32.5mCcm?2),asshowninTAHFPFigure1b,whichishighlyadvantageousforthepreparationofafor5sand(thededopedcounterionataisreductionPF?P(3-MTH)?lmwasdopedwith6?)atpotentialanoxidationof?0.2potentialVforof10+1.6s.TheVconductivesuperwettingcoating.Tothisend,adouble-layerWCAsPEDOT?P(3-MTH)?lmwaspreparedbysequentially?ofthedopedanddedoped?lmweremeasuredelectrodepositingPEDOTandP(3-MTH)onthesameITOforlmseveralwithACNminutes(2×underca.1mL)afterrinsingthe?andthendryingitatroomtemperatureelectrodefromrespectivemonomer-containingLiClOsolutions(seecurvesobtainedbyCVinFigureS2Supporting4/ACNunder2.8.Electro-WettingtheTransitionPotential.PropertiesowingN2.

AofsimplePEDOTelectro-wetting?P(3-MTH)Devicedevice

Information).Thehighlyporousandnanoscalerough

structure

14738

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

ofPEDOTwassuccessfullyretainedaftertheelectrodepositionofP(3-MTH)(Q=64.2mCcm?2;Figure1c).Thisresultcanbeattributedtothegrowth-orientinge?ectofthenetworkstructureofthePEDOT?lm.37Amagni?edimageshowsthattheporousstructureiscomposedofconductivepolymer?bersofabout100nm(Figure1d).Thismethodforthepreparationofhighlyporousnanostructuredπ-conjugatedpolymer?lmsmayalsobeusedinotherphotoelectrical?elds.40ThesurfacechemicalcompositionofPEDOT?P(3-MTH)wasdeterminedbyXPS(Figure2a).TherelativeintensityofthephotoelectronpeakofO(1s,532.8eV)inthespectrumofPEDOT?P(3-MTH)issigni?cantlylowerthanthatinthespectrumofthePEDOT?lm,con?rmingthattheoutermostlayerofthePEDOT?P(3-MTH)structureismainlycomposedofhydro-phobicP(3-MTH)moieties.3.2.ElectrochemicalPropertiesofPEDOT?P(3-MTH).TheelectrochemicalpropertiesofPEDOT?P(3-MTH)wereexamined.PEDOT?P(3-MTH)showedastrongelectro-chemicalresponse(Figure3a),andthepeakcurrentdensities[j,redoxpeakpairsattheoxidationpeak(pa)andthereductionpeak(pc)]wereproportionaltothepotentialscanrates?lm.41(Figure3b),indicatingthereversibleredoxprocessinthisThisresultindicatesthattheas-preparedPEDOT?P(3-MTH)retainedthehighredoxactivityofpolythiophenes.3.3.ReversibleWettabilitySwitchingundertheApplicationofaPotential.Theas-preparedPEDOT?P(3-MTH)couldbereversiblydopedanddedopedunderoxidationandreductionpotentials,?respectively,inanelectrolytesolutioncontainingClO4(Figure4a).TheWCAsinthedopedanddedopedstatesofthePEDOT?P(3-MTH)?lmweremeasured(Figure4b).Upondedopingatapotentialof?0.2V,this?lmdisplayedsuperhydrophobicity,asevidencedbyahighstaticWCAof162.4°±2°andalowwaterslidingangleof3.0°±1°(Figure4b,left,andMovieS1,SupportingInformation).ComparedwiththehydrophobicP(3-MTH)?lm(FigureS3b,left,SupportingInformation),thehighlyporousstructureofFigurethePEDOT?P(3-MTH)?lmsigni?cantlyenhancedthePEDOT4.?P(3-MTH)(a)Dopingin(oxidation)LiClOanddedoping(reduction)of

4/acetonitrilesolutionatpotentials

hydrophobicityofthesurfaceP(3-MTH)moietiesduetothebetweenproportionalMTH)?+1.2lmbetweenand?0.2162.4V.(b)°±WCA2°(left,switchingtop)andoftheca.PEDOT0°upon?P(3-the

31,32,38increaseofair/watercontactinterfaces(inaCassiestate).Notably,thehydrophobicityofPEDOT?alternate

P(3-MTH)?lmisalsohigherthanthatofourearlierPEDOT?(oxidation),applicationP(3-HTH)?lm(itsWCAisabout159.0°).37Thisresultmayslidinganglerespectively.ofpotentials

of3.0°±1In°(left,thededopedof?0.2

bottom).state,(reduction)and+1.2V

(c)Reversiblethe?lmhaswettabilityalow

beattributedtotheirmorphologydi?erences.AlthoughP(3-transitionMTH)hasashorteralkylsidechain,itsdouble-layer?lmbicity(dedopedofthestate)PEDOTand?P(3-MTH)superhydrophilicity?lmbetween(dopedsuperhydropho-state).

processesmoreabundantnanostructures,whichcanreducethecontactareabetweenthewaterdropletandtheinterface.31,32,38Onthecontrary,asuperhydrophilicPEDOT?P(3-MTH)?lmresultcon?rmedthatthedopantClO4?wasonlypresentinthecouldbeobtainedsimplybydopingthedouble-layer?lmatdopedPEDOT?P(3-MTH)?lm.Thedopingprocessaltered+1.2Vfor5sinanelectrolytesolutioncontainingClOthechemicalcompositionofthe?lmsurface,triggeringa

4?.AwaterdropletspreadrapidlyonthedopedPEDOT?P(3-wettabilitytransitionfromhydrophobictohydrophilic.17,27

MTH)?lm,resultinginaWCAofessentially0°(Figure4b,Whenawaterdropletwasdepositedonsuchadopedandright).TheresultsindicatethatthewettabilityofthePEDOT?highlyporousstructured?lm,itcouldrapidly?lltheinnerairP(3-MTH)?lmchangedfromsuperhydrophobicitytosuper-poresbeneathitduetoatwo-orthree-dimensionalcapillaryhydrophilicityuponapplyingtheoxidationpotential.e?ect14,42,43andconsequentlyshowedanultralowcontactWithregardtothemechanismofthewettingswitching,weangle.UpondedopingofthePEDOT?P(3-MTH)?lmat?0.2proposethatupondopingat+1.2V,thedopantClOVfor10s,thepolythiophenebackbonesofthe?lmreturnedtotheirneutralstate,andthedopantClOpositivelychargedpolythiopheneback-4?isintroducedintothe4?wasreleasedbackintothebonesofPEDOT?P(3-MTH)tocounterbalancethecharge,leadingtotheformation?17,41ofalargenumberofhydrophilic150lmelectrolyte°exhibited,indicatingasolution.17,41near-sphericalAthatthededopedshapewaterwithdroplet?lmaregainedWCAdepositedofmoreonthisitssuper-thandipoles(Figure4a).Ahigh-resolutionXPSspectrumhydrophobicstate.Therefore,reversibleswitchingoftheclearlyshowedthattheuniquephotoelectronpeakofCl(2p,wettabilitybetweensuperhydrophobicityandsuperhydrophi-207.0eV)wasonlyobservedforthedopedPEDOT?P(3-licityonthePEDOT?P(3-MTH)?lmwasrealizedbyMTH)?lmandnotforthededoped?lm(Figure2b).Thisalternatelyapplyingpotentialsof?0.2Vand+1.2V.

14739dx.doi.org/10.1021/am5043627|ACSAppl.Mater.Interfaces2014,6,14736?14743

Figure5.(a)WCAmeasurementsonPEDOT?P(3-MTH)underdi?erentpotentialsandthechangesinWCAduringtheincrease(◆,oxidationprocess)MTH),andandPEDOTdecrease?(□

lms,reductionobtainedprocess)atascaninratepotentialof200betweenmVs?1;?j0.2denotesand+1.2thecurrent

V.(b)Cyclicdensity.voltammogramsofthePEDOT?P(3-MTH),P(3-

Figuredenotes6.the(a)currentCyclicdensity.voltammogram(b)TheofWCAsthePEDOTofthe??P(3-MTH)lmafterdoping?lmatobtained+1.6Vatandascandedopingrateofat200?0.2mVVs?1

intheina0.20.2MMTAHFP/ACN

TAHFP/ACNsolution.solution;j

Figurespherical7.shape.(a)Randomly(b)DopeddistributedPEDOT?waterP(3-MTH)droplets?lm(4changedμL)onfromthereddishreddishbrownbrowntoPEDOTbluish?green.P(3-MTH)Water?dropletslm.Theseappliedwatertodropletsthis?lmshowwererapidlyalmostabsorbed.(c)UV/vismeasurementsofthe(reddishbrownline)dedopedand(bluishgreenline)dopedPEDOT?P(3-MTH)?lm.

showninFigure4c,thereversiblewettabilityswitchingprocessoxidationlevel(Figure5bandFigureS4,Supportingcouldberepeatedseveraltimesinthissystem.Information).ThisbehaviorimpliesthatthedopinglevelofInaddition,thewettingbehaviorisdependentonthedopingthePEDOTmoietiesdoesnotsigni?cantlyin?uencetheWCAlevelofthePEDOT?P(3-MTH),whichmaybepreciselyofthe?lm.However,arapiddecreaseinWCAfrommorethancontrolledbyadjustingthepotential.AplotofWCAasa150°toca.0°occurredwhentheappliedpotentialwasfunctionofthepotentialfrom?0.2to+1.2Visshowninincreasedfrom+0.6to+1.0V.ThisdecreaseinWCAFigure5a,whichcon?rmsthepotential-dependentwettabilitycorrespondsmainlytotheoxidationofsurfaceP(3-MTH)switchingofPEDOT?P(3-MTH).TheWCAremainedalmostmoietiesinPEDOT?P(3-MTH).Therefore,thewettabilityofunchangedwhenthepotentialwasincreasedfrom?0.2to+0.6PEDOT?P(3-MTH)stronglydependsonthedopinglevelofV.Duringdoping,PEDOTmoietiesinPEDOT?P(3-MTH)thesurfaceP(3-MTH)moieties.Whenthepotentialexceededwereoxidized,whileP(3-MTH)moietiesremainedatalow+1.0V,thesuperhydrophilicstateofPEDOT?P(3-MTH)