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2016Vol. 2 No. 2: 7

Research Article

DOI: 10.21767/2472-1123.100014

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Journal of Organic & Inorganic ChemistryISSN 2472-1123

Moronkola BA1, Alegbe MJ2, Eshilokun AO3, Giwa AO4 and Watkins GM1

1 Department of Chemistry, Rhodes University, PO Box 94, Grahamstown, South Africa

2 Department of Chemistry, University of Western Cape, South Africa

3 Department of Chemistry, University of Limpopo, Medunsa Campus, South Africa

4 InstituteofMarineBiotechnology,UniversityMalaysiaTerengganu,21030KualaTerengganu,Malaysia

Corresponding author: MoronkolaBA

[email protected]

Department of Chemistry, Rhodes University, PO Box 94, Grahamstown, South Africa.

Tel:+8130296678

Citation: MoronkolaBA,AlegbeMJ,EshilokunAO,etal.Electrospinning,FunctionalizationandQuaternizationofPolyvinylbenzylchloride(PVBC)ElectrospunNanofibers. JOrgInorgChem.2016,2:2.

IntroductionElectrospinning is the most versatile of all the methods formaking nanofibers. The method could be applied to virtuallyeverysolubleorfusiblepolymerandthepolymersolutionscanbemodifiedwithadditivespriortoorafterelectrospinningforspecialpurposes[1,2].Thoughtheelectrospinningtechniquecanbescaledupforcommercialproduction,itsproductivityhasbeena challenge [2]. There have therefore been many attempts toimproveontheproductivityoftheprocess.Improvedandmoreefficient versionsofelectro spinninghave recentlyevolvedbutthey all operateon thebasic principles of the techniques. Thedifferentversionscanbecategorizedundermononozzle,multinozzleandneedlelesselectrospinning.

Themononozzleisthesimplesttypeofelectrospinningsetupinwhichonlyonenozzle/needledischargesthepolymersolution.Mononozzleelectrospinningissimpleanddoesnotrequirealotofcapitalinvestment.Itsmajorlimitationisthelowproductivity.

In the multi nozzle electro spinning, the polymer solution isfed into an array of nozzles or needleswhich are either staticormoving [3,4].Uniformandbead-freenanofibersare formed

only when all the electrospinning parameters are optimized.However, it is difficult to check case-by-case whether all theparametersareoptimizedpriortoelectrospinnning.Optimizationof the electrospinning parameters could be checked duringelectrospinningusingthestabilityandshapeoftheTaylorconeorthepatternofnanofiberdeposition.

Thesurfaceof theelectrospunnanofibrecanbe functionalizedwith a ligand in order to create reactive sites that are specificto thedesiredbindingmoleculesoranalyteof interest [5]andalso, to enhance their absorption properties (chemical sensorsandbiosensors)andalsoextendtheirshelflife[6].Themoderntrendsinthefunctionalizationofnanofiberssuchastreatmentbyblending,coating,radiationwithelectromagneticwave,electronbeam,ironbeamandcoronaorplasmatreatmenthavealsobeenfoundusefulforthesynthesisofelectrospunnanofibers[7].

Electrospinning, Functionalization and Quaternization of Polyvinylbenzylchloride

(PVBC) Electrospun Nanofibers

AbstractThepolyvinylbenzylchloride(PVBC)waselectrospunintonanofibersina1:1(v/v)ratioofN,N-Dimethylformamide (DMF), Tetrahyhdrofuran solventmixture, thesurfacewas functionalizedusingethylenediamineandfinallyquaternizedPVBCusingthreedifferentalkylgroups(CH3, C2H5 and C3H7).Fouriertransforminfrared(FTIR)analysiswasusedtocharacterizethefunctionalgroupspresent.Thebandassignedto670cm-1

v(C-Cl)disappearedcompletelytoformanewbandat1562cm-1 indicatingthepresenceofNHgrouponthefibers.Energydispersivex-rayspectrometer(EDX)forPVBCshowsthepresenceofabroadpeakforClontheunfunctionalizedfiberandthispeakdisappearstoformasharppeakofnitrogenfrom the amine in ethylenediamine (EDA) of thefibers. X-raydiffraction (XRD)analysisofthefibersrevealsthesharppeakon40(2θ)degreeaxisonthesurfaceofthefunctionalizedfibers.Itwasalsoobservedthat,Brunauer,Emmett,Teller (BET)surfaceareaofthesorbentmaterials(PVBC)changedafterthefunctionalizationwithamine.

Keywords: Polyvinylbenzylchloride(PVBC);Ethylenediamine(EDA);Alkylgroups(CH3, C2H5 and C3H7)

Received: July01,2016; Accepted: July25,2016; Published: August01,2016

2016Vol. 2 No. 1: 7

ARCHIVOS DE MEDICINAISSN 1698-9465


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In thiscaseElectrospinpolyvinylbenzylchloride intonanofibers,postfunctionalizedwithethylenediamineandthenquaternized,usingthreedifferentalkylgroupstoproducedifferentnanofibersandcharacterizationofthesorbentmaterials.

Materials and MethodsMaterials polyvinylbenzylchloride (PVBC), N,N-Dimethylformamide (DMF), Tetrahyhdrofuran (THF),ethylenediamine (EDA), were purchased from Sigma Aldrich(Johannesburg, South Africa) and used as obtained. All thechemicalswereofanalyticalgrade.

Electrospinning of polyvinylbenzylchloride (PVBC)ThedifferentconcentrationsofPVBCfrom20,25,30,35,40and45wt%solutionswerepreparedina1:1(v/v)ratioofDMF:THFsolventmixture.Themixtureswerestirredatroomtemperatureovernight until a homogeneous solution was formed. It wasthentransferredintoasyringe.Thesyringewasconnectedtoanelectrospinningset-upconsistingofahighvoltagesupplyandanaluminumcollectingplate.Theflowrateofthepolymersolutionwascontrolledusingaprogrammablesyringepump.Thesolutionwaselectrospunatapositivevoltageof15kV,thetip-to-collectordistancewas15cmandtheflowratewas0.2mL/handalltheseconditionsgaveananofiber.Allprocedureswerecarriedoutatroomtemperature.

Post functionalization of polyvinylbenzylchloride (PVBC) nanofibers2.15gofPVBCnanofiberpresented in Figure 1.4(E)wascutoutincircularportionsof(1.5cm)ofthenanofibersheetsoakedin8.0gofethylenediamine(EDA)in15mLofethanolandshakenonamechanicalshakerforfivedays(Figure 1.0)andthereactioninthevesselwasallowedtoproceedat80-100°Cfor36hrsfortheaminationreaction.Afterthereaction,themodifiedfiberswereremovedfromthesolutionandthefiberswashedwithmethanol,Soxhletextractedwithmethanol,andthenairdried.

Quatenization of polyvinylbenzylchloride (PVBC)2.0 g each of the post functionalized polyvinylbenzylchloridewereprepared indifferent100mL reactionvessel.A50mLof

ethylenediaminewasintroducedintothe100mLvesselcontaining7.0gofmethyliodidein4.0goflutidineandethanolwasaddedinto100mLreactionvesselwithastirrerandwasshakenonamechanical shaker at 50°C to60°C for 24hrs. Thequaternizedfibrewas filtered under vacuum and,washed extensivelywithwater.Theiodinewasremovedbywashingthequaternizedfiberswith100mLof0.1MFeCl3in6MHCl,followedbyusingahot100mLof0.05MNa2S2O5solutionandfinally50mLofconc.HClwasusedtoprotonatethesitesandthefiberwasdriedinadesiccatorfor24hrs(sameprocedurewasusedforethylandproply).

FT-IR spectroscopyThe Fourier transform infrared (FT-IR) spectra of PVBC,functionalized PVBC and quaternized PVBC were obtainedusing a Perkin-Elmer Spectrum 100FT-IR spectrometerwith anAutoIMAGESystem.

Scanning electron microscopy (SEM)To determine the surface morphology of the PVBC, EDA andquaternized of PVBC, ground particles of each polymer weretakenanddustedontoa carbon sticker, then coatedwith goldusingasputtercoater(BalzersUnion,FL-9496)for30min.Imageswere recorded using INCAPentaFET3 (VegaTescan) SEM fittedwithanOxfordISISEDS.

Energy dispersive X-ray spectrometer (EDS)TheEDSiscoupledtoaScanningElectronMicroscope(SEM).TheobviousadvantageofEDSelementalanalysisoverconventionalchemicalanalysisisthat,elementalcompositionofselectedphasecanbeanalysedinabulksample.Inordertogetmorestructuralinformation and understanding on the adsorption mechanismoftheunfunctionalizedandthefunctionalizedPVBC,anenergydispersivex-rayspectrometer(EDS)wasusedtoinvestigatetheelementalcompositionofthefibers.TheEDSdetectsX-raysfromthe sample when excited by the highly focused, high-energy,primaryelectronbeam,penetratingintothesample.

X-ray diffraction analysis (XRD)Thistechniqueisusedtoidentifymineralphaseofasampleanditsparticlesize.OperatingconditionsofX-raydiffractionanalysis

Brunauer, Emmett, Teller (BET) analysisBrunauer,Emmett,Teller (BET)analysis involvescarbondioxideadsorption isotherms which were measured at 77K, usingMicrometricsASAP2020surfaceareaandporosityanalyzer.Prior

SEMimages (scalebar=20µm)showingthemorphologyof fibers electrospun from PVBC solutions atconcentrationof(e)35%w/v(f)40%w/v.(voltageof15Kvandataconstantspinningdistanceof15cm).

Figure 1.4

E F

The functionalization of polyvinylbenzylchloride-baseddiquaternaryammoniumnanofibresPVBC(R’=CH3, C2H5 and C3H7).

Figure 1.0

NH2(CH2)XNH2

Ethanol

n

Cr NH(CH2)XNH2

n

H3C N CH3

CH3 l

Ethanol

n

R’R’

R’ R’

Cr

Cr(CH2)XN N

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toeachmeasurement,thesamplesweredegassedforaminimumoftwoweekstoensurecompleteremovalofadsorbedimpurities.Degassing was performed at 70°C for the liner polymers andat150°Cforcross linkedpolymers.TheBETtheory [8]explainsthephysical adsorptionof gasmoleculeson solid surfaces andprovidesthebasisformeasurementofthespecificsurfaceareaof amaterial. Thebasic conceptof the theory is anexpansionof Langmuir theory, which deals with monolayer molecularadsorptionandamultilayeradsorptionbuilton thehypothesisthat,gasmoleculesareadsorbedonsolidlayersandthat,thereisnointeractionbetweeneachadsorptionlayer[9].

Results and DiscussionCharacterization studiesFTIR studies of unfunctionalized and functionalized PVBC:Thecharacteristic peaks in the spectrum (A) of the PVBC can beassignedasfollows:670cm-1

v(C-Cl),2976cm-1 corresponds to the

CH(CH3, C2H5 and C3H7),while1451cm-1spectrum represents the

CHbendingvibrationofthesameCHgroupinthealkylgroups.Afterthefunctionalization,thespectrumshowssomesignificantchanges.Thev(C-Cl)at670cm

-1disappearedcompletelytoformanewbandatpeaks1562cm-1whichcanbeassignedtoN-Hgroupoftheaminegroup,whilethepeaksatbetween1610and799cm-1areduetoC=OandC=Nstretchinggroups.Thepresenceofbandat3336cm-1isduetobondedOHgroups,whichindicatesthe presence ofwater of crystallization. According to the FTIRspectra, the location where the chemical reaction took placeduringthepreparationofPVBCmaybeproposedinFigure 1.1.

Scanning electron microscopy (SEM)Electrospinning is a technique thatutilizes theelectric force todrive polymer fluid and to produce polymer nanofibers. Theshear viscosity, electric conductivityand surface tensionof thepolymersolutionarethemostimportantpropertiesaffectingtheformationofnanofibers[10].

The increase in polymer concentration could adversely affectthecohesivenessof the liquid, thus leadingtoreduction inthesurfacetensionofthepolymerinsolution.

The SEM images of the 20 and 25% (w/v) electrospunnanofibersfor(PVBC)PVBCinN,N’-dimethylformamide(DMF),Tetrahydrofuran (THF) solution are shown in Figures 1.2a and 1.2b,adropletsprayoccurredandacontinuous jetofpolymerparticleswas formedatFigure 1.2a. The jet from lowviscositysolutionsbreaksupintodropletsduetotheloweramount20%w/vofpolymer.Atsolutionconcentrationof25,30,(w/v)PVBCin Figures 1.2b and 1.3c thepresenceof beadswasobserved,but thebeadswerecompletelydisappearedandthe formationofbeadfreefiberswereobservedwhentheconcentrationofthesolutionwasincreasedto40and45%w/v.Itisbelievedthat,therelativelyhighviscosity(30,40,45%w/v),oftheconcentrationsolution,voltageanddistancemadethemorphologyofthefiberto improve from bead to bead free fibers. The best optimumcondition for the morphology was observed with 45% (w/v)solution,withdiameter ranging from650-680nmandthiswassubjectedforpostfunctionalizationusingethylenediamine(EDA).

Figure 1.5g themorphologyof the45%w/velectrospunPVBCnanofibers was functionalized with EDA. The SEM images waspresented in Figure 1.5hwithaslightdifferencewithachangeinmorphologyduringfunctionalizationandthefiberswerenotdamaged.Thefiberdiameterrangewas665-769nm.ThisshowsaslightincreaseinthefiberdiameterafterthefunctionalizationwithEDA.

FTIR absorption spectra for the unfunctionalizedpolyvinylbenzylchloride(A),functionalizedPVBC(B)andthequaternizedPVBC(R’=CH3, C2H5 and C3H7)(C,DandE)nanofibres.

Figure 1.1

799 1610 3336

799

799

1610

1610

3336

3336

3336

1451

1451670

E

D

C

B

A1562

1000 2000 3000 4000Wavenumber (cm-1)

SEMimages(scalebar=20µm)showingthemorphologyof fibers electrospun from PVBC solutions atconcentration of (a) (particles) 20% w/v (b) (beaded)25%w/v. (voltageof15Kvandataconstantspinningdistanceof15cm).

Figure 1.2

A B

SEMimages(scalebar=20µm)showingthemorphologyof fibers electrospun from PVBC solutions atconcentrationof (c) (beaded)30%w/v (d) (beed free)35%w/v. (voltageof15Kvandataconstantspinningdistanceof15cm).

Figure 1.3

CC D

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AfterthefunctionalizePVBCinEDA,asshowninFigure 1.5h, the functionalizedfiberswerequaternizedusing,methyl,ethylandpropyliodide,inlutidineandethanoltogivetheSEMmorphologyin Figures 1.6I, 1.6j and 1.7k.

Energy dispersive X-ray spectrometer (EDS) used for PVBCTheEDSiscoupledtoaScanningElectronMicroscope(SEM).TheobviousadvantageofEDSelementalanalysisoverconventionalchemicalanalysisisthat,elementalcompositionofselectedphasecanbeanalysedinabulksample.Inordertogetmorestructuralinformation and understanding on the adsorption mechanismoftheunfunctionalizedandthefunctionalizedPVBC,anenergydispersivex-rayspectrometer(EDS)wasusedtoinvestigatetheelementalcompositionofthefibersasshowninFigures 1.8 and 1.9.TheEDSdetectsX-raysfromthesamplewhenexcitedbythehighlyfocused,high-energy,primaryelectronbeam,penetratingintothesample.ComparingEDSimagesofunfunctionalizedandfunctionalizedPVBC,Figure 1.8showsthepresenceofChlorineonthePVBC,theremovalofchlorineinFigure 1.9confirmsthatthefiberswerefunctionalizedwiththepresenceofNitrogenasclearlyobservedintheEDSspectraandthiswasincorroborationwithFT-IRresults.

SEMimages(scalebar=20µm)showingthemorphologyof of nanofibers (g) unfunctionalized fiber and (h)functionalized fiber with EDA, methyl iodide, lutidineandethanol.

Figure 1.5

G H

SEMimages(scalebar=20µm)showingthemorphologyof nanofibers (i) quaternized fiber with CH3 and (j)quaternizedfiberwithC2H5.

Figure 1.6

I J

SEMimages(scalebar=20µm)showingthemorphologyofofnanofibers(k)quaternizedfiberwithC3H7.

Figure 1.7

K

EDXspectraofunfunctionalizedPVBCnanofibre.Figure 1.8

0 1 2 3 4 5 6 7 8 9 10Full Scale 3774 cts Cursor: 0.000 keV

EDXspectraofquaternizedPVBCnanofibers.Figure 1.9

0 1 2 3 4 5 6 7 8 9 1 0KeVFull Scale 4385 cts Cursor: 0.000

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X-ray defraction analysis (XRD)Figure 2.0ashowsthespectrumofthePVBCwithabroadpeakat2 theata in2θdegreeaxis isassignedtocarbonbeforepostfunctionalizationwith EDA. The sharp peak onFigure 2 theata at40 in2θdegreeaxis isassignedtotheN in theNH3

+groupsonthesurfaceofthefunctionalizedPVBC[11]verifyingthat,theenhanced nitrogen content on the fiber surface was from theaminegroupsFigure 2.0b.

BET surface areaThe specific surface area of the sorbent defines its efficiencyfor adsorption. The surface area of unfunctionalized and thefunctionalizedPVBCnanofibermaterialsweremeasured, usingtheBETmethodandtheresultsarepresentedinTable 1.

Itwasobservedthat, thesurfaceareaofthesorbentmaterials(PVBC) changed after the functionalizationwith EDA. It canbeconcluded that the surface area of the sorbent materials wasreduced as shown in Table 2.

ConclusionInthisstudy,theelectrospinningofPVBCintoananofiberswereprepared,throughthemodificationoffibersurface,usingmultinitrogencontainingaminatingreagentsforPVBCandquaternizes

with R’ = CH3, C2H5 and C3H7, characterized using differentinstrumentssuchasFouriertransforminfrared(FTIR),ScanningElectronMicroscopy,EnergyDispersiveX-raySpectrometer(EDS),X-ray Defraction Analysis (XRD) and Brunauer, Emmett, Teller(BET)Analysis.Thelowcostsorbentmaterialwillbeeffectiveandserveasanalternativematerialfortheremovalofanionsfromaqueoussolutionsdueto the functionalgroupspresentonthequaternizedPVBC.

AcknowledgementsThe authors acknowledge the Department of Chemistry andElectronMicroscopy Unit, Rhodes University, for facilities andLagosstateUniversity,Nigeriaforgrantingstudyleavetothefirstauthor.

ShowstheXRDpatternoftheunfunctionalizedPVBC.Figure 2.0a

12000

10000

8000

6000

4000

2000

00 10 20 30 40 50 60 70 80 90

2θDegree

Inte

nsity

(a.u

)

ShowstheXRDpatternoftheunfunctionalizedPVBC.Figure 2.0b

12000

10000

8000

6000

4000

2000

00 10 20 30 40 50 60 70 80 90

2өDegree

Inte

nsity

(a.u

)

Parameter SettingsX-raydetector Vantec1

Generatorvoltage 40KvGenerator current 40Ma

Scanningrangeangle(θ) 10o-80o

Scanningtype Lockedcouple

Scan speed per step 2θ/minandstepsizeof0.02o Theta

Scantime 0.5secperstepScansize 0.03o

Synchronousrotation CopperKα(alpha)at1.540598

Table 1OperatingconditionsofX-raydiffractionanalysis.

Unfunctionalized PVBC Functionalized PVBC341.1m2/g 243.3m2/g

Table 2 BETsinglepointsurfaceareameasurementsforunfunctionalizedandfunctionalizedPVBCsorbentmaterials.

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