PMMA 溶剂,可调纤维形态

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AppliedSurfaceScience

journalhomepage:www.elsevier.com/locate/apsusc

TunablesurfacemorphologyofelectrospunPMMAfiberusingbinarysolvent

ZhiLiua,Jiang-huiZhaoa,PengLiua,Ji-huanHea,b,∗

ab

NationalEngineeringLaboratoryforModernSilk,CollegeofTextileandClothingEngineering,SoochowUniversity,199Ren-AiRoad,Suzhou215123,ChinaNantongTextileInstitute,SoochowUniversity,Nantong,China

article

info

abstract

Articlehistory:

Received24September2015Receivedinrevisedform10December2015

Accepted21December2015

Availableonline23December2015

Keywords:

BinarysolventElectrospinningPMMA

PhaseseparationSuperhydrophobic

Superhydrophobic–superoleophilicfibrouspolymethylmethacrylate(PMMA)membraneswerepre-paredbyelectrospinningtechnique.Themembranesexhibitedahighwatercontactangleupto153.9◦andnearlyzerooilcontactangle.Thissuperwettabilitypropertyisattributedtohierarchicalmacro-andnanostructureonsurfaceofPMMAmembraneandcanbeconvenientlytunedbyadjustingtheweightratioofbinarysolventofN,N-dimethylacetamideandacetone.ResultantfibrousPMMAmembraneswithsuperhydrophobic–superoleophilicpropertycanbeusedinwatertreatment.Thisfacileone-stepstrategyshowsanalternativeapproachtoproducespecialwettabilitysurfaceandwillbenefitthismaterial.

©2015ElsevierB.V.Allrightsreserved.

1.Introduction

Solidsurfacewithspecialwettabilityhasarousedintensiveresearchinthepasttwodecadesduetoitsimportantroleinindustry,agricultureanddailylife[1,2].Superwettabilitysurfaceswithrespecttowatercontactangle(WCA)/oilcontactangle(OCA)above150◦orbelow5◦showgreatprospectinpracticalindus-trialapplications,suchasself-cleaning[3],liquidtransportation[4],biochemicalseparation[5],andmicrofluidsystems[6].Inspiredbynaturalcreaturesandbasedonfundamentalresearches,itcanbetentativelyconcludedthatsuperwettabilitysurfacederivesfromtheirhierarchicalsurfacewithspecialtopographicalmorphol-ogyandchemicalcomponents[7,8].Accordingtothisprinciple,varioustechniqueshavebeenappliedsofartoconstructsuperwettabilitysurface,suchaselectrochemicaldeposition[9],tem-platesynthesis[10],coatingmethod[11]andelectrospinningmethod[12].Amongthem,electrospinningisbelievedafaciletechnologytoachievespecificgeometricalstructuresurface,andporousmembraneviaelectrospinningtechniqueexhibitsattractivefeaturesincludinghighspecificsurfacearea,internalconnectionofpores,controllablefiberdiameterandthickness.SinceJiang’sgroup[13]reportedelectrospunbeadedpolystyrenefiberwithsuperhydrophobicproperty,variousmaterialshavebeenfabricated

∗Correspondingauthor.

E-mailaddress:hejihuan@suda.edu.cn(J.-h.He).

throughelectrospinningtechniquetoobtainspecialwettabilitysurface.Forexample,Yoonetal.[14]constructedafibrousmem-branewithbead-on-stringstructurebyelectrospinning,andafterplasmatreatment,theWCAincreasedfrom141◦to158◦.Inspiredbysilverragwortsurface,Dingetal.[15]fabricatedPSnanofibreswithhierarchicalmacro-andnanostructurebyelectrospinning.Furthermore,electrospinningtechniquefollowedbyahydrophobicmodificationprocess,manyinorganicnanofiberswithsuperwett-abilitypropertieswasalsoobtained,suchasSiO2nanofiber[16],carbon-silicananofiber[17].

Recently,duetotheheatresistance,compatibilitywithhumantissueandgoodhydrophobicproperty,PMMAfibersfabricatedthroughelectrospinningtechniqueshowpotentialapplicationsinboneimplantsandwatertreatment.InPMMAelectrospinningprocess,varioussolventshavebeenusedtodissolvePMMAtoobtainregeneratedsolutions,suchasacetone[18],N,N-dimethylformamide[19],tetrahydrofuran[20],ethylacetate[21]andchloroform[22].Usingthesesolvents,differentPMMAfibermorphologyanddiameterwereobtained.PreviouselectrospunPMMAmembraneswereusuallyfabricatedusingsinglesolvent.Todate,limitedresearchesreportedbinarysolventforPMMAelec-trospinning,suchastrifluoroaceticacid/dichloromethane(weightratio1:1)[23]andchloroform/N,N-dimethylformamide(weightratio7:3)[24].However,effectsofvariedweightratioofthesebinarysolventsonspinningprocesswerenotdiscussed.Atthesametime,Miyauchietal.[25]reportedthatsolventweightratiosoftetrahydrofuran/dimethylformamideaffectthefibersurface

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structuresinpolystyreneelectrospinning.Qietal.[26]carriedoutabinarysystemsolventofnonsolvent/solventtodissolvepoly(l-lacticacid),achievingmicro-andnano-porousstructurenanofibersbyelectrospinning.Furthermore,otherresearcheshavealsoreportedthatporousstructureswereobtainedwhenusingabinarysolventintheelectrospinningprocess[27,28].Allofthesesuggestthatbinarysolventhaskeyeffectonelectrospinningpro-cessandformationofspecificsurfacestructure.

Tothebestofourknowledge,therearestillfewreportsstudyingtheeffectofbinarysolventonPMMAelectrospinning.Inthepresentstudy,variousweightratioofN,N-dimethylacetamide(DMAC)andacetone(ACE),10:0,8:2,6:4,5:5,4:6,2:8and0:10werecarriedouttoinvestigateeffectofbinarysolventonsolutionpropertiesandelectrospunPMMAmembranemorphology.Resultsshowedthatweightratioofbinarysolventinfluencethespinability,fiberdiam-eterandfibersurfacemorphology.JustvaryingtheweightratioofDMAC/ACE,superwettabilitysurfaceofelectrospunPMMAmem-braneswithWCA/OCAof153.9◦and0◦canbeobtained,indicatingpotentialapplicationsinwatertreatmentofthismaterial.

2.Experimental

2.1.Materials

Polymethylmethacrylate(PMMA,Mw=350,000gmol−1)waspurchasedfromAladdinIndustrialCorporation,Shanghai,China.N,N-dimethylformamideandAcetoneweresuppliedbySinopharmChemicalReagentCo.,Ltd.(Suzhou,China).Allreagentswereana-lyticalgradeandwereusedasreceivedwithoutfurthertreatment.

2.2.PreparationofPMMAsolutions,electrospunPMMAfibermembraneandcastingPMMAfilms

PMMAwasdissolvedinbinarysolventofDMAC/ACEwithweightratioof10:0,8:2,6:4,5:5,4:6,2:8and0:10,respectively.Thentheywerestirredforabout10hatroomtemperature,toachievetransparentsolutionswithPMMAconcentrationof12wt.%.Inelectrospinningexperiment,ahighelectricpotentialof15kVwasappliedtothedropletofPMMAsolutionatthetipofasyringeneedle(0.8mmininternaldiameter).TheelectrospunPMMAnanofibreswerecollectedonflataluminumfoilwhichwasplacedatadistanceof15cmfromthesyringetip.Aconstantvolumeflowrateof0.8ml/hwasmaintainedusingasyringepump.TwohourswerecontrolledtoobtainelectrospunPMMAfibermembrane.Theambientrelativehumidityandtemperatureusedinthespinningprocesswere50±2%and25±2◦C,respectively,andkeptconstant.TocomparewithPMMAfilmspreparedbycastingmethod,the12wt.%PMMAsolutionswithbinarysolventofDMAC/ACE(weightratioof6:4,5:5,4:6,2:8and0:10)werecastonglassdishes(90mmindiameter).Thentheyweredriedinadryovenat50◦Cfor6h.TheresultantPMMAfilmswerecutintocircles(3cmindiame-ter)forwettabilitymeasurement.Thethicknessoftheelectrospunmembraneandcastingfilmwasmeasuredusingamicrometerfor5timesatdifferentlocationsandlistedinTable2.

2.3.Measurementandcharacterization

Solubilityparameterofasolventistheaffinityindicatorbetweenpolymerandsolvent.Themeasureofaffinitiesbetweenpolymer(1)andsolvent(2)isthesolubilityparameterdistance,Ra,whichwasfirstdevelopedbySkaarup.TheRaisbasedontheHansensolubilityparametersbythefollowingequation:

Ra=[4(ıd2−ıd1)2+(ıp2−ıp1)2

+(ıh2−ı21/2

h1)]

whereıdisthedispersivecontribution,ıpisthepolarcontribution,ıhisthehydrogenbondingcontribution.Table1liststhesolubilityparametersofDMAC,ACEandPMMA.

ThemorphologyofelectrospunPMMAfibersandPMMAinregeneratedsolutionswasobservedusinganSEM(HitachiS-4800,Tokyo,Japan)at20◦C,60RH.TopreparethePMMAsamplesinregeneratedsolutionsforimaging,PMMAsolutionsof0.01wt.%werepreparedbydilutingthePMMAsolutionswithaccordantweightratioofDMAC/ACE.Then2␮LofthedilutedPMMAsolutionwasdroppedontofreshsiliconsurfacesanddriedinair.Samplesweresputter-coatedwithgoldlayerpriortoimaging.Thediam-etersofPMMAfiberswerecalculatedbymeasuringatleast100fibersatrandomusingImageJprogram.

Rheologicalstudieswerecarriedoutonarheometer(AR2000,TAInstruments,andAmerica)witha40mmconeplate(Ti,40/2◦).Thenormalforceappliedonthesampleduringfallingofthetopplatewaslimitedto0.1N.Theshearratewaslinearlyincreasedfrom0.1to50001/sat25◦C.

Theelectricalconductivityofthesolutionwasmeasuredbyaconductivitymeter(DDS-307A,ShanghaiInstrument&ElectricSci-entificInstrumentCo.,Ltd.,China).Theprocesswasperformedatleastfivetimesinthetest.ThesurfacetensionofthesolutionwithdifferentweightratioofDMAC/ACEwasmeasuredusingtheWil-hemyplatemethodonadigitalDataPhysics®Tensiometer(Model:DCAT21,Germany)atroomtemperature.Thespeedoftheliftmotorusedindetectingthesurfaceoftheliquidwas1.00mms−1.Thetestwasstoppedwhenthestandarddeviationofsurfacetensionwassmallerthan0.03mNm−1overthelast50measurementcycles.ThewettingpropertiesofwaterdropletsontheresultantPMMAsurfacewereevaluatedusinganopticalcontactanglemetersys-tem(KrüssDSA100,Germany).Thevolumesofdropletsusedforthewatercontactanglewas6␮L.Theresultantvaluesweretheaverageoffivedropletsatdifferentlocations.

3.Resultsanddiscussion

3.1.MorphologyanddiameterofPMMAfibersatconcentrationof12wt.%.

Interestingly,withthedecreasedweightofDMACandtheincreasedweightofACE,itshowsthreesignificantchanges:(1)thefibermorphologychangesfrombeadstouniformfibers;(2)thefibersurfacemorphologychangesfromhierarchicalmacro-andnanostructuretosmoothsurfacegradually;(3)thefiberdiameterincreasesfrom0.8±0.10␮mto4.8±0.56␮m,asshowninFig.1.Thechangeoffibermorphologyfrombeadsonlytofibersonlyinelectrospinninghasbeenrepeatedlymentionedinliteratures[31].Ingeneral,beadsonlyresultfromnotenoughentangle-mentsofmolecularchainsatlowpolymerconcentrationandfibersonlyresultfromahighconcentrationaboveacriticalpolymerconcentration,inthespinningprocess[32].UndersamePMMAconcentrationinthiscontribution,theincreasesofpolymervis-cositiesgradually(Fig.2)meantheincreaseofmolecularchainentanglements,whichleadstothechangeoffibermorphologyfrombeadsonlytofibersonly.

Inelectrospinningprocess,phaseseparationmechanismisbelievedtogoverntheformationofspecialsolidsurfaceinclud-ingporousandhierarchicalmacro/nanostructure.Itiswellknownthathighvolatilityofsolventorsolventsystemisimportanttoinducephaseseparation[33].However,Luoetal.[34]arguedthatbinarysolventsystemofhighsolubility/non-solvent(neitherofwhicharehighvolatility)alsocontributedtophaseseparationandhighlyporouselectrospunfiber.Meanwhile,someresearchesbelievethathighrelativehumidityisthekeyfactortocausephaseseparation[27],whileotherspresentthatlowhumiditycanalso

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Table1

Boilingpoint(B),electricalconductivity(E),surfacetension(S)ofDMACandACE.SolubilityparametersofDMAC,ACEandPMMA.ıt:totalsolubilityparameter,whichisdefinedasıt2=ıd2+ıp2+ıh2[29].

MaterialsDMACACEPMMA

B(◦C)16656.5–

E(␮s/cm)0.50.058–

S(mN/m)25.324.0–

ıd(Mpa0.5)16.815.518.6

ıp(Mpa0.5)11.510.410.5

ıh(Mpa0.5)10.27.07.5

ıt(Mpa0.5)[30]22.120.122.7

Ra4.66.2–

Fig.1.MorphologyanddiameterofelectrospunPMMAfiberwithdifferentweightratioofDMAC/ACE,withsolutionconcentrationof12wt.%.

Fig.2.RheologicalbehaviorofregeneratedPMMAsolutionswithbinarysolventofDMAC/ACE10:0,8:2,6:4,5:5,4:6,2:8,and0:10.

Fig.3.SolutionelectricalconductivityandsurfacetensionofregeneratedPMMAsolutions,withsolventweightratioofDMAC/ACE6:4,5:5,4:6,2:8,and0:10.

inducephenomenaofphaseseparation[35].Therefore,phasesep-arationmechanismisstillambiguous.Forvariouscircumstances,itshouldbemodifiedaccordingly.Inthepresentwork,DMAC(lowvolatility)andACE(highvolatility)(Table1)werecarriedouttodissolvePMMA,andelectrospinningprocessproceededatambi-entconditionof25±2◦C,50±2RH.AsshowninFig.1,thesurfacemorphologyvariedwithdifferentweightratioofDMAC/ACE.Andat6:4,resultantPMMAfiberexhibitedwrinkledsurfacewithnano-sizegrooveandridgestructurealongthefiberaxis.Suchmicro-andnanoscalesurfacestructureiscrucialtoachievingsuperhy-drophobicityofPMMAmembrane.Themechanismwastentativelyconcludedasfollows.Ononehand,duringelectrospinningpro-cess,thermodynamicinstabilitytookplaceduetothedecreaseoftemperatureandlossofsolventwiththerapidevaporationofACE.Thusthepolymericjetmightyieldtodifferentphase

structures:polymer-rich(PMMA)phaseandsolvent-rich(DMAC)phase;andfurtherevaporationofresidualDMACledtoridgeandgroovestructure(Fig.1).Ontheotherhand,duringspinningpro-cess,thechargedjetsubjectedtosomeinstabilitiesresultinginpulsationandspiralmotionofchargedjets[36,37],whichaccu-mulatedphaseseparation.Simultaneously,hierarchicalridgeandgroovestructuregrewalongthefiberaxisduetopolymericjetcontinuouslystretchedbyelectrostaticforce.Consequently,hier-archicalmacro-andnanostructurefibrousPMMAmembranewasobtained.WithvariedweightratioofDMAC/ACE,surfacemor-phologychangesfromhierarchicalstructuretosmoothstructure,indicatingdecreaseddegreeofphaseseparation.Inaddition,theincreasedrheologicalbehavior(Fig.2)anddecreasedsolutionsur-facetension(Fig.3)inthepresentstudyalsofavormorphologychangefromhierarchicalstructuretosmoothstructure,whichisinaccordancewithpreviousstudy[38].

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Fig.4.SuperhydrophobicityofelectrospunPMMAfibers,(a)WCAofelectrospunPMMAfiberswithsolventweightratioofDMAC/ACE6:4,5:5,4:6,2:8,0:10;(b)morphologyofelectrospunPMMAfiberswithsolventweightratioof6:4;(c)opticalimageofwaterdropletsonelectrospunPMMAfibers(6:4),thevolumeofwaterdropletis10␮L;(d)WCA;and(e)OCAofelectrospunPMMAfibers(6:4).

3.2.SolutionpropertiesofregeneratedPMMAsolutions

3.2.1.RheologicalbehaviorofsolutionsandPMMAmorphologyinsolutions

WithvariedweightratioofDMAC/ACE,electrospunPMMAfiberexhibitedchangeablefiberdiameter,thoughthePMMAconcen-trationandotherspinningparameterskeptconstant.Normally,solutionpropertygovernsthemorphologyofelectrospunfiber.Toinvestigatethechangeofanomalousfiberdiameter,solutionpropertiesincludingrheologicalbehavior,PMMAmorphologyinsolutions,electricalconductivityandsurfacetensionwerestud-iedintensively.AsshowninFig.2,itexhibitedsteadyincreaseofviscosities(from10:0to4:6),followedbysharpincrease(2:8and0:10)withdecreasedweightratioofDMACandincreasedweightratioofACE.Additionally,theweightratioof2:8and0:10showedshearthickeningbehavioratlowshearrate(Fig.2).Differently,shearthickeningbehaviorwasobservedatrelativelyhighshearrate(from10:0to4:6)(Fig.2).Itcanbespeculatedthatrecon-structedPMMAmacromolecularchainstructureduringshearingprocessleadstoincreaseofviscousresistance,subsequently,result-inginshearthickeningbehavior.Therheologicalbehaviorisanindicatorformacromoleculeentanglementsinsolutionandmacro-moleculeentanglementsisdeterminedbymacromoleculestateinsolutions[39].Therefore,themorphologyofPMMAintypicalsolu-tionsof6:4and2:8werepresentedinFig.S1.Itcanbeseenclearlythatin2:8solutionsphericalPMMAaggregatedtogether,forminggeometrypatterns,butrelativelysmallersizeofsphericalPMMAspreading,respectively,wasobservedin6:4solution.Thus,the2:8solutionsexhibitedhigherviscosityduetomoremoleculesentan-glementsintheshearingprocess,comparedwithsolutionsfrom10:0to4:6.

Thissolutionviscositychangeisaccordancewiththesolubil-ityparametersofDMAC,ACEandPMMA.Itiswellknownthatsolubilityparametersaretheaffinityindicatorsbetweenpolymerandsolvent,andthedegreeofaffinitiesbetweenpolymerandsol-ventisdeterminedbythesolubilityparameterdistance,Ra.AsshowninTable1,theRabetweenPMMAandDMACisshorterthanPMMAandACE,whichmeansthatDMACisthe‘good’sol-venttoPMMAcomparedwithACE(the‘poor’solvent).The‘good’solventindicatesalowdegreeofmacromoleculechainsoverlapandaggregationinsolutions,leadingtolowersolutionviscosity,subsequently,leadingtosmallerfiberdiameter[40].Oppositely,theACE(‘poor’solvent)suggestshigherdegreeofmacromoleculechainsoverlapandaggregationinsolutions,whichpreventsthe

Fig.5.WCAofPMMAfilmswithsolventweightratioofDMAC/ACE6:4,5:5,4:6,2:8,0:10;theinsertfigureisthefilmwithdiameterof3cm.

polymerchainsflowing,favoringtheincreaseofsolutionviscosity.Therefore,withtheincreaseofACE,solutionviscosityincreased.

3.2.2.ElectricalconductivityandsurfacetensionofregeneratedPMMAsolutions

Duringelectrospinningprocess,exceptfortherheologicalbehaviorofsolution,electricalconductivityandsurfacetensionalsoindispensablyaffectelectrospunfibermorphology,especiallythefiberdiameter.AsshowninFig.3,itwasobservedthatbothsolutionelectricalconductivity(from31.32to24.81␮s/cm)andsurfacetension(from1.52to0.97mN/m)decreasedgraduallywithdecreasedweightratioofDMACandincreasedweightofACE.Ingeneral,thedecreaseofsurfacetensionleadstothinnerdiameterwhilethedecreaseofelectricalconductivityfavorsincreasedfiberdiameter[41].Itcanbepredictedthatthesetwofactors,accompanywithincreasedsolutionviscositiesaresynergisticeffectonelectro-spinningprocess,resultinginincreaseddiameterofelectrospunPMMAfiber.

3.3.SuperhydrophobicityofelectrospunPMMAfibers

Specificsurfacemorphologyalwaysshowssuperanti-wettability.Fig.5showstheWCAofelectrospunPMMAmembrane

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Table2

Thickness(␮m)ofelectrospunPMMAmembraneandcastingPMMAfilms.

Sample

ElectrospunCasting

12%(6:4)56±2.2282±5.4

12%(5:5)78±3.1293±7.2

12%(4:6)95±3.7285±5.9

12%(2:8)128±4.5304±6.3

12%(0:10)157±4.8297±8.1

14%(6:4)98±3.6–

14%(4:6)137±5.2–

14%(0:10)164±4.8–

Fig.6.Morphology,diameterandwettabilitypropertiesofelectrospunPMMAfiberswithsolutionconcentrationof14wt.%.

withvariedweightratioofDMAC/ACE.AscanbeseeninFig.4,relativelydecreasedWCAwasobservedfrom153.9◦to129.8◦withweightratioofDMAC/ACEfrom6:4to0:10.ThesurfacemorphologyanddiameterofPMMAfibersplayacrucialroleinthewettabilityofresultantfibrousPMMAmembrane.Gener-ally,smallerdiameteroffibershowslowerwatercontactangleduetolimitedairtrappedbetweenmembraneandwater[42].However,inthepresentcase,thePMMAmembraneshavehie-rarchalmacro/nanostructure,especiallywhentheweightratioofDMAC/ACEis6:4(Fig.4b).Extremelyroughsurfacewithabout80–420nmridgesalongthePMMAfibersurfacewereobservedonthemembrane.Thishierarchicalmacro/nanostructureissimilartostructureofsilverragwortleafwhichhaswrinkledsurfacewithself-cleaningability[43].CassieandBaxterlawarguethathydrophobicityisrelatedtothecontactareabetweensolidsurfaceandwater,thatis,thelesscontactarealeadingtolargercontactangle[44].TheroughsurfaceofPMMAfiberwithmacro/nanostructurereducesthecontactareabetweenmembranesurfaceandwater,endowingthemembranesuperhydrophobicitywithWCAupto153.9◦(Fig.4c).Naturally,relativesmoothsurfaceofPMMAmembranesuchas0:10showedlowerWCA(129.8◦)becauseoflagercontactareabetweenmembranesurfaceandwater,comparedwith6:4.ComparedwithelectrospunPMMAmembrane,PMMAfilmspreparedbycastingmethodshowedlowerWCA(lowerthan107◦)(Fig.5).Additionally,resultantPMMAmembraneexhibitedsuperwettabilitypropertywithbothsuperhydrophobicityandsuperoleophilicity,asshowninFig.4c–e,suggestingpotentialapplicationsinwatertreatmentsuchasoil–waterseparation(Table2).

diameter,upto4.9±0.45␮mand8.42±0.63␮m,respectively.Itsuggeststhatweightratioofbinarysolventhascrucialeffectonsurfacemorphologyandfiberdiameter.

Similarly,theroughsurfaceofnano-sizegroovesonthesurfaceofPMMAfiber(6:4)suggestslesscontactareabetweenmembraneandwater(Fig.6).Therefore,the6:4membraneexhibitedhigherWCA(151.3◦)than4:6(144.5◦)and0:10(141.7◦).

Comparedwith12wt.%PMMAconcentration,the14wt.%PMMAconcentrationshowedsimilarWCAat6:4and4:6.However,for0:10,theWCAof14wt.%PMMAconcentrationis141.7◦largerthanthe12wt.%of129.8◦.For0:10,both12wt.%and14wt.%con-centrationshowedsmoothfibersurface.Then,thefiberdiametergovernsthesurfacewettabilityproperty.Thehigherfiberdiameter(0:10in14wt.%)leadstolargeWCA,whichwasaccordancewithpreviousstudy[42].

Infact,itwasdifficulttofabricatePMMAfiberin14wt.%con-centration,especiallyfor4:6and0:10.Itwaseasytojamtheneedleintheelectrospinningprocess,whichnothappenedin12wt.%con-centration.Additionally,theOCAofPMMAfibermembranewas0◦,indicatingpotentialapplicationinoil/waterseparation.

Therefore,justvaryingweightratioofbinarysolvent,superwettabilitysurfaceofPMMAmembranecanbeeasilyobtained.AnalternativewaytofabricationofsuperhydrophobicandsuperoleophilicelectrospunPMMAmembraneisBubbfilspinning,whichwasdevelopedfrombubbleelectrospinningformass-production[45].

4.Conclusions

3.4.MorphologyanddiameterofElectrospunPMMAfibers

Tofurtherverifythisapproach,PMMAmembraneswithcon-centrationof14wt.%werefabricatedbyelectrospinningwithrepresentativeweightratioofDMAC/ACE6:4,4:6and0:10,undersameconditions(Fig.6).Similarphenomenonwasobservedcom-paredwithPMMAconcentrationof12wt.%.The6:4showedwrinkledsurfacewithsmallestfiberdiameter(2.3±0.44␮m),but4:6and0:10presentedrelativesmoothsurfacewithhigherfiber

WithdecreasedweightofDMACandincreasedweightofACE,theviscositiesofPMMAsolutionsincreasedwhileelectricitycon-ductivityandsurfacetensiondecreased,whichcollectivelyledtotheincreaseofelectrospunPMMAfiberdiameter.Comparedwithchangeofpolymerconcentration,variedweightratioofbinarysolventundersamepolymerconcentrationdevelopsareplace-ablestrategytoobtainwide-sizedistributionofelectrospunfiberdiameter.Meanwhile,superhydrophobicandsuperoleophilicelec-trospunPMMAmembranecanbeobtainedbysimplyadjustingtheweightratioofbinarysolvent.Weexpectthatthisfacileprocesscan

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bereadilyadoptedforthefabricationofwidediameterdistributionofelectrospunnanofiberandforthedesignofsuperwettabilitysurface.

Acknowledgement

TheworkissupportedbyPriorityAcademicProgromDevel-opmentofJiangsuHigherEducationInstitutionsChina,NationalNaturalScienceFoundationofChinaunderGrantNo.11372205andProgectforSixKindsofTopTalentsinJiangsuProvinceunderGrantNo.ZBZZ-035,Science&TechnologyPillarProgramofJiangsuProvinceunderGrantNo.BE2013072.

[18]S.Piperno,L.Lozzi,R.Rastelli,M.Passacantando,S.Santucci,PMMA

nanofibersproductionbyelectrospinning,Appl.Surf.Sci.252(2006)5583–5586.

[19]A.V.Bazilevsky,A.L.Yarin,C.M.Megaridis,Co-electrospinningofcore-shell

fibersusingasingle-nozzletechnique,Langmuir23(2007)2311–2314.[20]G.Kwak,G.H.Lee,S.H.Shim,K.B.Yoon,Fabricationoflight-guiding

core/sheathfibersbycoaxialelectrospinning,Macromol.RapidCommun.29(2008)815–820.

[21]G.Guo,D.Yang,C.Wang,S.Yang,“Fishing”polymerbrushesonsingle-walled

carbonnanotubesbyin-situfreeradicalpolymerizationinapoorsolvent,Macromolecules39(2006)9035–9040.

[22]G.Y.Han,B.Guo,L.W.Zhang,B.S.Yang,Conductivegoldfilmsassembledon

electrospunpoly(methylmethacrylate)fibrousmats,Adv.Mater.18(2006)1709–1712.

[23]J.Zhang,F.H.Maurer,M.Yang,InsituformationofTiO2inelectrospun

poly(methylmethacrylate)nanohybrids,J.Phys.Chem.C115(2011)10431–10441.

[24]P.Gupta,C.Elkins,T.E.Long,G.L.Wilkes,Electrospinningoflinear

AppendixA.Supplementarydata

Supplementarydataassociatedwiththisarticlecanbefound,intheonlineversion,athttp://dx.doi.org/10.1016/j.apsusc.2015.12.176.

References

[1]M.J.Liu,L.Jiang,Switchableadhesiononliquid/solidinterfaces,Adv.Funct.

Mater.20(2010)3753–3764.

[2]X.Zhang,F.Shi,J.Niu,Y.G.Jiang,Z.Q.Wang,Superhydrophobicsurfaces:from

structuralcontroltofunctionalapplication,J.Mater.Chem.18(2008)621–633.

[3]X.Zhou,Z.Zhang,X.Xu,X.Men,X.Zhu,Fabricationofsuper-repellentcotton

textileswithrapidreversiblewettabilityswitchingofdiverseliquids,Appl.Surf.Sci.276(2013)571–577.

[4]A.Winkleman,G.Gotesman,A.Yoffe,R.Naaman,Immobilizingadropof

water:fabricatinghighlyhydrophobicsurfacesthatpinwaterdroplets,NanoLett.8(2008)1241–1245.

[5]K.Liu,X.Yao,L.Jiang,Recentdevelopmentsinbio-inspiredspecial

wettability,Chem.Soc.Rev.39(2010)3240–3255.

[6]A.I.Neto,C.A.Custodio,W.L.Song,J.F.Mano,High-throughputevaluationof

interactionsbetweenbiomaterials,proteinsandcellsusingpatternedsuperhydrophobicsubstrates,SoftMatter7(2011)4147–4151.

[7]Y.Zhang,Y.Chen,L.Shi,J.Li,Z.Guo,Recentprogressofdouble-structuraland

functionalmaterialswithspecialwettability,J.Mater.Chem.22(2012)799–815.

[8]K.Liu,L.Jiang,Bio-inspireddesignofmultiscalestructuresforfunction

integration,NanoToday6(2011)155–175.

[9]F.Shi,Z.Q.Wang,X.Zhang,Combiningalayer-bylayerassemblingtechnique

withelectrochemicaldepositionofgoldaggregatestomimicthelegsofwaterstriders,Adv.Mater.17(2005)1005–1009.

[10]G.Zhang,D.Y.Wang,Z.Z.Gu,H.Mohwald,Fabricationofsuperhydrophobic

surfacesfrombinarycolloidalassembly,Langmuir21(2005)9143–9148.

[11]A.Nakajima,K.Abe,K.Hashimoto,T.Watanabe,Preparationofhard

super-hydrophobicfilmswithvisiblelighttransmission,ThinSolidFilms376(2000)140–143.

[12]Z.Liu,C.H.He,S.Z.Zhang,L.Zhao,Amathematicalmodelfortheformationof

beadedfibersinelectrospinning,Therm.Sci.19(2015)1151–1154.

[13]L.Jiang,Y.Zhao,J.Zhai,Alotus-leaf-likesuperhydrophobicsurface:aporous

microsphere/nanofibercompositefilmpreparedbyelectrohydrodynamics,Angew.Chem.33(2004)4438–4441.

[14]Y.I.Yoon,H.S.Moon,W.S.Lyoo,T.S.Lee,W.H.Park,Superhydrophobicityof

PHBVfibroussurfacewithbead-on-stringstructure,J.ColloidInterfaceSci.320(2008)91–95.

[15]J.Lin,Y.Cai,X.Wang,B.Ding,J.Yu,M.Wang,Fabricationofbiomimetic

superhydrophobicsurfacesinspiredbylotusleafandsilverragwortleaf,Nanoscale3(2011)1258–1262.

[16]J.M.Lim,G.R.Yi,J.H.Moon,C.J.Heo,S.M.Yang,Superhydrophobicfilmsof

electrospunfiberswithmultiple-scalesurfacemorphology,Langmuir23(2007)7981–7989.

[17]M.H.Tai,P.Gao,B.Y.L.Tan,D.D.Sun,J.O.Leckie,Highlyefficientandflexible

electrospuncarbon-silicananofibrousmembraneforultrafastgravity-drivenoil–waterseparation,ACSAppl.Mater.Interfaces6(2014)9393–9401.

homopolymersofpoly(methylmethacrylate):exploringrelationships

betweenfiberformation,viscosity,molecularweightandconcentrationinagoodsolvent,Polymer46(2005)4799–4810.

[25]Y.Miyauchi,B.Ding,S.Shiratori,Fabricationofasilver-ragwort-leaf-like

super-hydrophobicmicro/nanoporousfibrousmatsurfacebyelectrospinning,Nanotechnology17(2006)5151.

[26]Z.Qi,H.Yu,Y.Chen,M.Zhu,Highlyporousfiberspreparedbyelectrospinning

aternarysystemofnonsolvent/solvent/poly(l-lacticacid),Mater.Lett.63(2009)415–418.

[27]C.L.Casper,J.S.Stephens,N.G.Tassi,D.B.Chase,J.F.Rabolt,Controllingsurface

morphologyofelectrospunpolystyrenefibers:effectofhumidityand

molecularweightintheelectrospinningprocess,Macromolecules37(2004)573–578.

[28]P.Dayal,J.Liu,S.Kumar,T.Kyu,Experimentalandtheoreticalinvestigations

ofporousstructureformationinelectrospunfibers,Macromolecules40(2007)7689–7694.

[29]A.K.Hołda,I.F.Vankelecom,IntegrallyskinnedPSf-basedSRNF-membranes

preparedviaphaseinversion–partB:influenceoflowmolecularweightadditives,J.Membr.Sci.450(2014)499–511.

[30]J.Liu,T.Liu,S.Kumar,EffectofsolventsolubilityparameteronSWNT

dispersioninPMMA,Polymer46(2005)3419–3424.

[31]S.Feng,Y.Hou,Y.Chen,Y.Xue,Y.Zheng,L.Jiang,Water-assistedfabrication

ofporousbead-on-stringfibers,J.Mater.Chem.A1(2013)8363–8366.[32]M.Essalhi,M.Khayet,Self-sustainedwebsofpolyvinylidenefluoride

electrospunnano-fibers:effectsofpolymerconcentrationanddesalinationbydirectcontactmembranedistillation,J.Membr.Sci.454(2014)133–143.[33]M.Bognitzki,W.Czado,T.Frese,A.Schaper,M.Hellwig,M.Steinhart,J.H.

Wendorff,Nanostructuredfibersviaelectrospinning,Adv.Mater.13(2001)70–72.

[34]C.J.Luo,M.Nangrejo,M.Edirisinghe,Anovelmethodofselectingsolventsfor

polymerelectrospinning,Polymer51(2010)1654–1662.

[35]L.Li,Z.Jiang,M.Li,R.Li,T.Fang,HierarchicallystructuredPMMAfibers

fabricatedbyelectrospinning,RSCAdv.4(2014)52973–52985.

[36]D.H.Reneker,A.L.Yarin,H.Fong,S.Koombhongse,Bendinginstabilityof

electricallychargedliquidjetsofpolymersolutionsinelectrospinning,J.Appl.Phys.87(2000)4531–4547.

[37]A.L.Yarin,S.Koombhongse,D.H.Reneker,Bendinginstabilityin

electrospinningofnanofibres,J.Appl.Phys.89(2001)3018–3026.[38]H.Fong,I.Chun,D.H.Reneker,Beadednanofibersformedduring

electrospinning,Polymer40(1999)4585–4592.

[39]F.Zhang,B.Zuo,Z.Fan,Z.Xie,Q.Lu,X.Zhang,D.L.Kaplan,Mechanismsand

controlofsilk-basedelectrospinning,Biomacromolecules13(2012)798–804.[40]D.K.Sharma,J.Shen,F.Li,ReinforcementofNafionintopolyacrylonitrile

(PAN)tofabricatethemintonanofibermatsbyelectrospinning:

characterizationofenhancedmechanicalandadsorptionproperties,RSCAdv.4(2014)39110–39117.

[41]M.Ma,R.M.Hill,Superhydrophobicsurfaces,Curr.Opin.ColloidInterfaceSci.

11(2006)193–202.

[42]M.Wang,D.Fang,N.Wang,S.Jiang,J.Nie,Q.Yu,G.Ma,Preparationof

PVDF/PVPcore–shellnanofibersmatsviahomogeneouselectrospinning,Polymer55(2014)2188–2196.

[43]Z.Z.Gu,H.M.Wei,R.Q.Zhang,G.Z.Han,C.Pan,H.Zhang,Z.M.Chen,Artificial

silverragwortsurface,Appl.Phys.Lett.86(2005)201915.

[44]G.McHale,N.J.Shirtcliffe,M.I.Newton,Contact-anglehysteresison

super-hydrophobicsurfaces,Langmuir20(2004)10146–10149.

[45]C.H.He,X.W.Li,P.Liu,Y.Li,BubbfilspinningforfabricationofPVAnanofibers,

Therm.Sci.19(2015)743–746.