Superhydrophobic Bilayer Coating Based on Annealed Electrospun Ultrathin Poly(-caprolactone)

15 Pages·2017·13.51 MB·English

coatings
Article
Superhydrophobic Bilayer Coating Based on
Annealed Electrospun Ultrathin Poly(ε-caprolactone)
Fibers and Electrosprayed Nanostructured Silica
Microparticles for Easy Emptying
Packaging Applications
JulianaLasprilla-Botero1,2,SergioTorres-Giner2,MariaPardo-Figuerez2,3,
MónicaÁlvarez-Láinez1andJoseM.Lagaron2,* ID
1 DesignEngineeringResearchGroup(GRID),ProductDesignEngineeringDepartment,UniversidadEAFIT,
Carrera49No7sur-50,Medellín050022,Colombia;jlaspril@eafit.edu.co(J.L.-B.);
malvar26@eafit.edu.co(M.Á.-L.)
2 NovelMaterialsandNanotechnologyGroup,InstituteofAgrochemistryandFoodTechnology(IATA),
SpanishCouncilforScientificResearch(CSIC),CalleCatedráticoAgustínEscardinoBenlloch7,
46980Paterna,Spain;[email protected](S.T.-G.);[email protected](M.P.-F.)
3 BioiniciaR&DDepartment,BioiniciaS.L.,CalleAlgepser65,46980Paterna,Spain
* Correspondence:[email protected]
(cid:1)(cid:2)(cid:3)(cid:1)(cid:4)(cid:5)(cid:6)(cid:7)(cid:8)(cid:1)
(cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:7)
Received:1April2018;Accepted:30April2018;Published:3May2018
Abstract:Acoatingrenderingsuperhydrophobicpropertiestolow-densitypolyethylene(LDPE)films
usedinpackagingapplicationswashereingeneratedbymeansoftheelectrohydrodynamicprocessing
(EHDP)technique. Tothisend,electrospunultrathinpoly(ε-caprolactone)(PCL)fibers,followedby
electrosprayednanostructuredsilica(SiO )microparticles,weredepositedontopoftheLDPEfilm.
2
Variouselectrospinningandelectrosprayingtimesweretestedandoptimizedfollowedbyathermal
post-treatmenttoprovidephysicaladhesionbetweenthebilayercoatingandtheLDPEsubstrate.
The morphology, hydrophobicity, permeance to limonene, and thermal stability of the resultant
nanostructuredcoatingswerecharacterized. Itwasobservedthatbycontrollingboththedeposition
timeoftheelectrospunultrathinPCLfibersandtheelectrosprayedSiO microparticles,aswellas
2
theconditionsofthethermalpost-treatment,effectivesuperhydrophobiccoatingsweredeveloped
ontotheLDPEfilms. Theresultantmultilayerpresentedahierarchicalmicro/nanostructuredsurface
with an apparent contact angle of 157◦ and a sliding angle of 8◦. The addition of silica reduced,
tosomeextent, thelimonene(aroma)barrier, likelyduetotheincreasedsurface-to-volumeratio,
whichallowedpermeantsorptiontooccurbutimprovedthethermalstabilityoftheLDPE/PCLfilm.
Asaresult,thedevelopedmultilayersystemofLDPE/PCL/SiO hassignificantpotentialforusein
2
easy-to-emptypackagingapplicationsofhighwateractivityproducts.
Keywords: electrospinning;electrospraying;PCL;Silica;coatings;foodpackaging
1. Introduction
Superhydrophobic coatings present surfaces with water contact angles larger than 150◦ and
slidinganglesoflessthan5◦[1]. Theyhavegainedpopularityoverthelastfewdecadestoimprovethe
currentcapabilitiesofmaterialsurfacesforapplicationsinwaterrepellency,self-cleaning,packaging,
etc.[2].Specifically,theuseofsuperhydrophobiccoatingshasbeenwidelyemployedinfoodpackaging
applicationstocontroldesiccationinfruitsandvegetablesandpreventmoistmigrationorevenflavor
losses. Thesecoatingsrepresentanattempttomimictheintrinsichydrophobicbehaviorsobserved
Coatings2018,8,173;doi:10.3390/coatings8050173 www.mdpi.com/journal/coatings
Coatings2018,8,173 2of15
in nature, where structural polysaccharides containing water-repellent properties preserve leaves
or fruits internally [3]. In addition, the phenomenon of superhydrophobicity has been popularly
observedintheleavesfromlotusandsilverragwort[4]. Toachievesuperhydrophobicityonsynthetic
surfaces,thechemicalandphysicalcompositionsofthesurfaceatboththemicro-andnanoscalesmust
beefficientlydesigned. Varioussuperhydrophobicsurfacecoatingshavebeenrecentlypreparedby
eithermodifyingthechemistryofthesurfacetorenderhydrophobicproperties[5,6]orbycreating
nanometer-scalefeaturesonmicro-roughenedsurfacesusingdifferenttechniques, suchasplasma
treatment, chemical etching, layer-by-layer (LbL) deposition, chemical vapor deposition (CVD),
micropatterningbylithography,and,morerecently,electrohydrodynamicprocessing(EHDP)[1,4,7].
Some of the above-mentioned fabrication methods, such as micropatterning by lithography,
chemicaletchingorplasmatreatment,areusuallycomplicatedsincetheyrequireamultistepapproach
and are not versatile in terms of designing certain surface parameters to obtain a desired coating.
In other cases, they can be restricted due to the fact that the superhydrophobic property is not
suitableorpermanentsincethecoatingsdonotcovertheentiresurfaceorcanbeeasilydamaged.
Alternatively,theuseofEHDPforbothelectrospinningandelectrosprayingprocesses,hasprovento
beastraightforwardmethodologyformanufacturingmicro-andnanoscalestructuresfromawide
varietyofpolymermaterialsinaflexibleandcontrolledmanner[8]. Suchtechniquescanparticularly
allowthefabricationofdifferentpolymer-basedstructuresandassembliesinthepackagingfield[9],
in which some of them can additionally display a high degree of complexity in terms of surface
morphologyandtopology[1].
Inthissense,theelectrospinningtechniquehasshownconsiderablesuccessinmanufacturing
polymer nanofibers mats for repelling a wide range of liquids [6,7,10–12]. Electrospun nanofibers
intrinsically provide at least one length scale of roughness for superhydrophobicity due to their
ultrathindimensions[7]. Likewise,electrosprayinghasalsoreceivedagreatdealofattentionduetoits
abilitytoproduceeitherpolymerorinorganicsmallparticles,downtothesubmicronsize.Thesemicro-
andsubmicronparticlesareconsideredmoreefficientforachievinganuniformsurfacecoveragedue
to their small size, allowing a thin and uniform coating to be obtained on films, which ultimately
resultsinbetterbarrierproperties[13].
Nowadays, novel andmultifunctionalpolymer/inorganicnanostructuredcoatingswithdifferent
surfacemorphologiesandwettabilities,rangingfromhydrophobictosuperhydrophobic,areproduced
byEHDP[1,14–16]. Thecommonprocedurebeginswiththefabricationofapolymertemplatemadeof
electrospunfibers,whichisthencoveredwithhydrophobicparticlespreparedbyelectrospraying[1,4,15–17].
Thismethodologyhasgainedinterestduetotheformationofcompositemembraneswithdifferentsurface
morphologies,resultinginawiderangeofapplicationsfordifferentsectors,suchasmembranetechnology,
packaging,automotive,tissueengineering,andenergystorage[18].
AlthoughtheuseofEHDPtodevelophighlyhydrophobiccoatingsiscertainlyverypromising,
thepooradhesionoftheelectrosprayedparticlestotheelectrospunfibrilarmembranesisaninherent
problemthatrestrictsthepracticalapplicationofthesecoatings. Thus,thisissueneedstobesolved
inordertoretainthehydrophobicitypropertyofthewholesurface,especiallyinflexiblepackaging
applications[1]. Furthermore,thedepositionofnanoparticlesandfibercoatingsontoplasticsurfaces,
asisthecaseinlow-densitypolyethylene(LDPE)films,hasproventobechallengingbecauseofthe
lowsurfaceenergyandnon-polarnatureofthepolyolefins[19].
LDPEfilmsarewidelyemployedinthepackagingindustry,especiallyinpackagingapplications
wheretheireasy-to-emptypropertycouldbeofasignificantadvantagefordevicesliketoothpaste,
pouches or bottles. Hence, one of the most significant challenges for the production of LDPE
films is generating a flexible material that is capable of obtaining complete coverage of the target
areawhilstkeepinghighbarrierpropertiestopreventwatermigrationthroughit[3,13].Although
superhydrophobic LDPE surfaces have been prepared from polymer synthesis [5] and by surface
treatment with corona discharge and tetrafluoromethane (CF ) plasma [5,19,20], these treatments
4
Coatings 2018, 8, x FOR PEER REVIEW 3 of 15
tCreoaattinmgse2n0t1 8w,8i,t1h7 3corona discharge and tetrafluoromethane (CF4) plasma [5,19,20], these treatm3eonft1s5
have only shown a very superficial and short-term effect. In addition, they are expensive, technically
complex and are often limited by the nature and geometry of the substrate.
haveonlyshownaverysuperficialandshort-termeffect. Inaddition,theyareexpensive,technically
Herein, for the first time, a methodology to fabricate mechanically-resistant and thermally-stable
complexandareoftenlimitedbythenatureandgeometryofthesubstrate.
superhydrophobic nanostructured bilayer coatings prepared by EHDP to be applied on LDPE or
Herein,forthefirsttime,amethodologytofabricatemechanically-resistantandthermally-stable
other packaging films is reported. To accomplish this, a commercial LDPE film was initially coated
superhydrophobicnanostructuredbilayercoatingspreparedbyEHDPtobeappliedonLDPEorother
bpya cakna geinlegctfirolmspsuins rmepaotr toefd .uTltoraatchcionm ppolilsyh(εt-hcaisp,raoclaocmtomnee)r c(iPalCLLD) PfEibefirlsm. wThaesni,n ihtiyadllryopcohaotbeidc bSyiOan2
particles were electrosprayed on the PCL mat to develop a hierarchical micro/nanostructure surface.
electrospunmatofultrathinpoly(ε-caprolactone)(PCL)fibers. Then,hydrophobicSiO particleswere
2
Thereafter, an annealing process, that is, a thermal post-treatment below the polymer’s melting point
electrosprayedonthePCLmattodevelopahierarchicalmicro/nanostructuresurface. Thereafter,
(aTnm)a, nwnaesa alipnpglipedro tcoe sins,crtehaastei tsh,ea ptohteernmtiaall upsoasbt-itlriteya tomf ethnet dbeevloewlopthede cpoomlypmoesirt’es bmy eplthiynsgicpaol ibnitnd(Ting) ,
m
the silica particles to the polymer fibrous mesh and substrate and, thus, allowing physical interlayer
wasappliedtoincreasethepotentialusabilityofthedevelopedcompositebyphysicalbindingthesilica
adhesion.
particlestothepolymerfibrousmeshandsubstrateand,thus,allowingphysicalinterlayeradhesion.
22.. EExxppeerriimmeennttaall
22..11.. MMaatteerriaialsls
CCoorroonnaa--ttrreeaatteedd LLDDPPEE ffiilmlmss wwitithh tthhicickknneesssseess oof f115500 µµmm wweerree kkiinnddlyly pprroovviiddeedd bbyy LLaajojovvicic TTuubbaa
EEmmbbaallaažžaa, ,dd.o.o.o.o. (.Lj(uLbjuljbalnjaan, Sal,oSvleonviean).i aP)C.LP, CwLit,hw ai tnhumabneurm avbeerraagvee mraogleecmuloalre wcueliagrhwt (eMigNh) tof( M80N,0)0o0f
g8/0m,0o0l0, agn/dm 1-obl,utaanndol1 (-abnuhtayndorolu(asn, 9h9y.8d%ro puus,ri9ty9.)8 w%erpeu broittyh) pwuercrehabsoetdh frpoumrc Mhaesrecdk KfrGomaAM (DeracrkmKstGadatA,
G(Deramrmanstya)d. tC, hGloerrmofaonrmy) .(Cpuhrliotryo f>o r9m9.5(%pu) rwityas> p9u9r.c5h%a)sewda fsropmur cPhaansreedacf rQomuimPaicnar eSa.cAQ. (uBiamrcicealoSn.aA, .
S(pBaairnce).l oHnyad,Sroppaihno)b.iHc ypdyrroopgheonbici cSpiOyr2o ngaenniocstSriuOc2tunraendo smtriucrcotupraerdticmleisc r(oHpDarKti cHle1s8()H wDiKthH a1n8 )awveitrhagaen
paavretricalgee spizaer toicfl ecas.i z1e7o µfmca .a1n7dµ am BarunndaauBerr–uEnmaumere–tEt–mTemlleetrt –(TBeEllTe)r s(BuErfTa)ces uarrfeaac eoaf r1e7a0o–f213700 m–223/g0 mwe2/reg
owbetareineodb tfarionmed WfarockmerW Cahcekmeire CChoemmpiaenCy o(Mmupnaincyh, (GMeurmniacnhy,)G. Tehrme panaryt)i.clTe hsiezep aanrtdic sleizes idziestarinbdutsioizne
odfi stthreib puutirocnhaosfetdh eSpiOu2r cphaarsteicdleSsi Ow2eprea ratincalelyszweder ebya nlaalsyezr eddifbfyralcatsioenr dwififtrha ctthioen ewquitihpmtheenet qMuiaplmveernnt
MMaasltveerrsnizeMr aMstSe2rs0i0z0e r(MMaSl2v0e0r0n (PManalavlyertincaPla, nMaalylvtiecranl,, MUKal)v (esrene, UFiKgu)r(ese 1e).F Aiglul rmea1t)e.rAialllsm waetereri aulssewd earse
ruesceedivaesd rweciethivoeudt wfuirtthhoeur tpfuurritfhiceartpiounr.i fi cation.

FFiigguurree 11.. PPaarrttiiccllee ssiizzee ddiissttrriibbuuttiioonn ooff tthhee ssiilliiccaa ((SSiiOO2) )mmicicrrooppaarrtitcicleless, ,aass rreecceeiviveedd. .
2
2.2. Fabrication of the Nanostructured Coating
2.2. FabricationoftheNanostructuredCoating
2.2.1. Electrospinning of PCL Fibers onto LDPE Films
2.2.1. ElectrospinningofPCLFibersontoLDPEFilms
In the first stage, a layer of electrospun PCL fibers was deposited onto the corona-treated LDPE
Inthefirststage,alayerofelectrospunPCLfiberswasdepositedontothecorona-treatedLDPE
films. To this end, a PCL solution was prepared by dissolving 10 wt % of the polymer in a solvent
films. Tothisend,aPCLsolutionwaspreparedbydissolving10wt%ofthepolymerinasolvent
mixture containing 1-butanol and chloroform at 5:1 (v/v) ratio whilst magnetically stirring at room
mixturecontaining1-butanolandchloroformat5:1(v/v)ratiowhilstmagneticallystirringatroom
temperature until complete dissolution was achieved.
temperatureuntilcompletedissolutionwasachieved.
The resultant PCL solution was then transferred to a 5-mL plastic syringe connected through a
TheresultantPCLsolutionwasthentransferredtoa5-mLplasticsyringeconnectedthrougha
PTFE tube to a stainless steel needle (0.603 mm nominal ID—20 G with a blunt tip) and electrospun
PTFEtubetoastainlesssteelneedle(0.603mmnominalID—20Gwithablunttip)andelectrospun
using a pilot-plant Fluidnatek™ LE-500 apparatus (Bioinicia S.L., Valencia, Spain) with relative
using a pilot-plant Fluidnatek™ LE-500 apparatus (Bioinicia S.L., Valencia, Spain) with relative
humidity (RH) and temperature control. This was operated in lab mode with only one emitter in
humidity (RH) and temperature control. This was operated in lab mode with only one emitter in
scanning mode by setting a voltage of 10 kV, a flow-rate of 2 mL/h, and a tip-to-collector distance of
scanningmodebysettingavoltageof10kV,aflow-rateof2mL/h,andatip-to-collectordistance
10 cm. During this process, the LDPE film was attached to the roll-to-roll collector so that the fibers
of 10 cm. During this process, the LDPE film was attached to the roll-to-roll collector so that the
Coatings2018,8,173 4of15
Coatings 2018, 8, x FOR PEER REVIEW 4 of 15
fibewresrwe ceoreatceoda dteirdecdtilrye cotnlytoo an stomaalsl mreacltlanregcutalanrg puolratriopno ortfi othne ocfotrhoenac-otrreoantae-dt rteoapt esdidteo pof stihdee foilfmth. Tehfiel m.
Theexepxepreimrimenetsn twsewree rpeerpfeorrfmoremd eadt 2a5t °2C5 a◦nCda 3n0d%3 R0%H. RH.
2.22.2.2..E2.l eEcltercotrsopsrparyaiynigngo foSf iSOiO22P Paarrtitcicleless oonnttoo LLDDPPEE//PPCCLL FFilimlms s
SecSoencodnldy,lyth, ethSei OSi2Om2 micircorpoparatritcilcelessw weerreee eleleccttrroosspprraayyeedd oonn tthhee pprreevviioouusslyly pprreeppaareredd LLDDPPEE/P/CPLC L
filmfilsm. Ts.h Teheel eecletrcotrsopsrparyaiynigngs osolulutitoionnw waassp prreeppaarreedd bbyy ddiissppeerrssiinngg tthhee SSiOiO2 2mmicircorpoapratirctliecsle ast a1t w1tw %t %in in
1-b1u-tbauntaonloalt arto oromomte mtempepreartauturerew whhilisltstm maaggnneettiiccaallllyy ssttiirrrriinngg ffoorr ttwwoo hhoouurrss. .TThehreeraefateftre, rt,hteh seosluotluiotnio n
wawsuasl turaltsroansoicnaicteadtedfo fro5r 5m minini nina annU Ultltrraattuurrrraaxx TT2255 bbaassiicc ffrroomm IIKKAA-W-Weerrkkee GGmmbHbH && CoC.o K.GK G(St(aSutafeunf,e n,
GeGrmeramnayn)yto) taoc ahciehvieevae sat satbalbelea nanddh hoommooggeenneeoouuss SSiiOO22 ddiissppeerrssiioonn. .
ThTehper eppraerpeadreSdiO S2iOd2i sdpiseprseirosniown awsatsh ethreeareftaefrteerl eecltercotrsopsrparyaeydedon otnh tehbei lbaiylaeyreLrD LPDEP/EP/PCCLLfi flimlm,o, nonth e
sidtehoe fstihdee aolrf etahdey adlreepaodsyit eddepeolescitterods peluenctrfiobseprus.nT foibtehriss. eTnod ,ththise seanmd,e tFhleu isdanmaet eFkl™uidLnEa-t5e0k0™e qLuEip-5m00e nt
equipment described above was used by setting a voltage of 7.6 kV, a flow-rate of 1.1 mL/h, and a
describedabovewasusedbysettingavoltageof7.6kV,aflow-rateof1.1mL/h,andatip-to-collector
tip-to-collector distance of 15 cm. The rest of the conditions were the same as those used for the PCL
distanceof15cm. TherestoftheconditionswerethesameasthoseusedforthePCLlayer.
layer.
2.2.3. ThermalPost-Treatment
2.2.3. Thermal Post-Treatment
ThemultilayerLDPE/PCL/SiO filmswereannealedundertheoptimalconditionsof55◦Cfor
2
1min(sTeeheS emcutilotinla3y.e1r) LbDyPaEp/pPrCoLa/cShiOin2g fitlhmest woperpel aantenteoaltehde ubnodtteor mthep olaptteimwailt hcoonudtiatipopnlsy oinf g55p °rCe sfsour r1e muisnin g
(see Section 3.1) by approaching the top plate to the bottom plate without applying pressure using a
ahydraulichot-press(model-4122fromCarver,Inc.,Wabash,IN,USA).Sampleswereplacedbetween
hydraulic hot-press (model-4122 from Carver, Inc., Wabash, IN, USA). Samples were placed between
Teflonsheetsinordertoprotectthematerialsfromdirectcontactwiththehotplates.Figure2illustrates
Teflon sheets in order to protect the materials from direct contact with the hot plates. Figure 2 illustrates
thestep-by-stepmethodologyfollowedtopreparethenanostructuredmultilayerLDPE/PCL/SiO
the step-by-step methodology followed to prepare the nanostructured multilayer LDPE/PCL/SiO2 2
film. Delaminationbetweenthecoatingandthesubstrateoccurredbeforetheannealingprocesswas
film. Delamination between the coating and the substrate occurred before the annealing process was
carriedout;however,thiswasnotthecaseafterannealing,wherethecoatedLDPEfilmscouldnot
carried out; however, this was not the case after annealing, where the coated LDPE films could not
bedelaminatedbyhand. Theannealingprocessbelowthemeltingpointhasbeenprovenbeforeto
be delaminated by hand. The annealing process below the melting point has been proven before to
promoteinterfibercoalescenceandhence,physicaladhesion/lamination,evenbetweenmaterialsthat
promote interfiber coalescence and hence, physical adhesion/lamination, even between materials that
areanreo tnocht echmeimcaicllayllcyo cmompaptaibtilbele[2 [12]1.].

Figure 2. Schematic illustration of (1) deposition of the electrospun poly(ε-caprolactone) (PCL) fibers
Figure 2. Schematic illustration of (1) deposition of the electrospun poly(ε-caprolactone) (PCL)
fibeorns othne thloewlo-dwe-ndseitnys iptyolpyeotlhyyeltehnyel e(nLeD(PLED) PfEil)mfi, lm(2,) (2d)epdoespiotisointi oonf othfeth eeleecletrcotsropsrapyready esdilsicilai c(aSi(OSi2O) )
2
micmroicproaprtaicrtliecsleosn otnh ethLeD LPDEP/EP/PCCLLfi flimlm,,a anndd( 3(3))t htheerrmmaall aannnneeaalliinngg ooff tthhee LLDDPPEE//PPCCLL/S/iSOi2O filmfil mwiwthi tah a
2
hot press without applying pressure.
hotpresswithoutapplyingpressure.

2.3. FilmCharacterization
2.3.1. OpticalandScanningElectronMicroscopy
The morphologies of the electrospun fibers and resultant films were determined via light
microscopy (Eclipse 90i, Nikon, Tokyo, Japan) using a 40× objective as well as a field emission
scanningelectronmicroscope(FESEM,HitachiS-4800fromHitachiHighTechnologiesCorp.,Tokyo,
Japan). BeforeFESEMobservation,thefilmsampleswerecryofracturedusingnitrogenliquidand
Coatings2018,8,173 5of15
subsequentlysputteredwithagold-palladiumlayerfor3minundervacuumpriortoanalysis.Samples
wereobservedusinganelectronbeamaccelerationvoltageof10kV.Microanalysis, performedby
energy-dispersiveX-rayspectroscopy(EDS,HitachiHighTechnologiesCorp.,Japan),wasusedto
verify the presence and composition of the inorganic particles. Fiber and particle diameters were
determinedandaveragedusingImageJ1.50isoftwareforanalysis.
2.3.2. WaterContactAngleMeasurements
Thewettabilityofthefilmsampleswasevaluatedbythemeasurementoftheapparentwater
contact angle (WCA) using a manual optical tensiometer in a Video-Based Contact Angle Meter,
ThetaLiteTL101model,fromBiolinScientific(Espoo,Finland). Datawereobtainedbyanalyzingthe
shapeofadistilledwaterdropof5µLplacedoverthesamplesurface,takenafter5sofdroplet–surface
contact.Measurementswerecarriedoutunderroomconditions. Imageanalysesweretakenbymeans
oftheOneAttensionsoftwarev3.1(BiolinScientific)andtheWCAvaluereportedforeachsample
was the average of five measurements at different regions of each sample. The sliding angle was
determinedona5-µLwaterdropletdepositedoverthesurfacerecordedwithavideowhilebeing
tilted and analyzed with the online software Ergonomics Ruler of the Universitat Politècnica de
València(UPV),Valencia,Spain(https://www.ergonautas.upv.es/herramientas/ruler/ruler.php).
2.3.3. PermeabilityTest
ThethicknessesofallfilmsweremeasuredusingadigitalmicrometerAlfaMirageAbsoluteseries
S00014,fromMitutoyoCorporation(Kawasaki,Japan),having±0.001mmaccuracy. Measurements
wereperformedatfiverandompositionsandvalueswereaveraged.
TheD-Limonenepermeanceofthefilmsampleswasdeterminedusingthegravimetricmethod
(ASTME96-95[22]). Briefly,5mLofD-limonenewasplacedinsideaPaynepermeabilitycupwitha
diameterof3.5cmfromElcometerSprl(Hermalle-sous-Argenteau,Belgium). Thefilmwasintroduced
inthecupsbeingexposedtotheD-limonenevaporonthecoatedsideandsecuredwithsiliconrings
underenvironmentalconditionsof25◦Cand40%RH.Thecupswereweightedperiodicallyusingan
analyticalbalance(±0.0001g). Identicalcupswithaluminumfoilswereusedascontrolsamplesto
estimatethevaporlossthroughthesealing. TheD-Limonenepermeationratewasdeterminedfrom
thesteady-statepermeationslopeobtainedfromaregressionanalysisofweightlossdataperunit
areavs. time,inwhichtheweightlosswascalculatedasthetotalcelllossminusthelossthroughthe
sealing. TheD-LimonenepermeancewasobtainedbycorrectingtheD-Limonenepermeationratefor
thepermeantpartialpressure. Threereplicatesperfilmsampleweredeterminedandaveraged.
2.3.4. ThermogravimetricAnalysis
Thethermalstabilitywasanalyzedbythermogravimetricanalysis(TGA)inaTGAmodelQ-500
fromTAinstruments(NewCastle,DE,USA).Filmsampleswithaweightbetween12–16mg,wereheated
from25to900◦C,ataheatingrateof10◦C/minunderanitrogenflowrateof60mL/min.
2.3.5. DifferentialScanningCalorimetry
ThermalanalysesoftheelectrospunPCLfibermatwascarriedoutonaDSC7analyzerfrom
PerkinElmer, Inc. (Waltham, MA, USA). The thermal program was applied from −20 to 100 ◦C
inanitrogenatmosphereusingarefrigeratingcoolingaccessory(Intracooler2, PerkinElmer, Inc.).
Thescanningratewas10◦C/mininordertominimizetheinfluenceofthisparameteronthethermal
properties. Anemptyaluminumcupwasusedasthereference. Calibrationwasperformedusingan
indiumsample. Theendothermicrunswerecarriedoutinatleasttriplicate. Fromthefirstheating
ramp, the melting point of the PCL fiber mats was measured to be at 58.7 ◦C, in accordance with
previouswork[23].
Coatings 2018, 8, x FOR PEER REVIEW 6 of 15
2.3.5. Differential Scanning Calorimetry
Thermal analyses of the electrospun PCL fiber mat was carried out on a DSC 7 analyzer from
PerkinElmer, Inc. (Waltham, MA, USA). The thermal program was applied from −20 to 100 °C in a
nitrogen atmosphere using a refrigerating cooling accessory (Intracooler 2, PerkinElmer, Inc.). The
scanning rate was 10 °C/min in order to minimize the influence of this parameter on the thermal
properties. An empty aluminum cup was used as the reference. Calibration was performed using an
indium sample. The endothermic runs were carried out in at least triplicate. From the first heating
ramp, the melting point of the PCL fiber mats was measured to be at 58.7 °C, in accordance with
Coatings2018,8,173 6of15
previous work [23].
3.3 R.eRseuslutslt asnadn dDDisicsucsussisoino n
3.31..1 O. Optpimtimizaiztaiotnio nofo tfhteh TehTehremrmala PloPsots-Tt-rTeraetamtmenent tonon thteh ePPCCLL CCoaotaitning g
Inordertopromotethedesiredhydrophobicity,alayerofelectrospunPCLfiberswassuccessfully
In order to promote the desired hydrophobicity, a layer of electrospun PCL fibers was
depositedontotheLDPEfilms. Figure3highlightsthemorphologyofthePCLfibers,asdetermined
successfully deposited onto the LDPE films. Figure 3 highlights the morphology of the PCL fibers, as
byopticalmicroscopy(Figure3A),aswellasbyFESEM(Figure3B).Themicroscopyresultspointto
determined by optical microscopy (Figure 3A), as well as by FESEM (Figure 3B). The microscopy
well-formed,bead-free,ultrathinfiberswithanaveragefiberdiameterofca. 3µm.
results point to well-formed, bead-free, ultrathin fibers with an average fiber diameter of ca. 3 µm.

(A) (B)
FiFgiugruer e3. 3(.A()A O)pOtpictaicl amlmicricorsocsocpoyp yimimagaeg oefo tfhteh eeleecletrcotrsopsupnu npoployl(yε(-εca-cparporloalcatoctnoen)e ()P(CPLC)L f)ibfiebresr tsatkaekne nata t
404×0. ×(B.)( BFi)eFldie ledmeimssiisosnio sncasncanninngin egleecltercotrno mnimcriocrsocsocpoep (eF(EFSEESMEM) i)mimagaeg eofo tfhteh ePCPCLL fifibebresr statkakenen aat t11000000××. .
Initially, a thermal treatment optimization step was performed on the PCL electrospun fibers
Initially, athermaltreatmentoptimizationstepwasperformedonthePCLelectrospunfibers
coated with LDPE to render adhesion to the substrate and maximize the contact angle. Table 1
coatedwithLDPEtorenderadhesiontothesubstrateandmaximizethecontactangle.Table1indicates
indicates that, interestingly, the electrospun fibers were able to promote a higher apparent contact
that,interestingly,theelectrospunfiberswereabletopromoteahigherapparentcontactanglethan
angle than LDPE. However, after the thermal treatment, this hydrophobic enhancement was reduced.
LDPE.However,afterthethermaltreatment,thishydrophobicenhancementwasreduced. Thermal
Thermal treatment promotes inter-material adhesion in the ultrathin fibers; however, the inter-fiber
treatmentpromotesinter-materialadhesionintheultrathinfibers;however,theinter-fiberroughness
roughness may diminish, hence decreasing the apparent water contact angle of the structure. Thus,
maydiminish,hencedecreasingtheapparentwatercontactangleofthestructure. Thus,themicrofiber
the microfiber structure was lost due to fibers’ coalescence or even melting, especially when the
structurewaslostduetofibers’coalescenceorevenmelting,especiallywhenthethermaltreatment
thermal treatment was applied at higher temperatures than the PCL melting point of the fibers and
was applied at higher temperatures than the PCL melting point of the fibers and for longer times.
for longer times. This feature prevents the formation of superhydrophobic surfaces by just coating
ThisfeaturepreventstheformationofsuperhydrophobicsurfacesbyjustcoatingwithelectrospunPCL
with electrospun PCL fibers. As a result, additional topographical features were created by adding
fibers. Asaresult,additionaltopographicalfeatureswerecreatedbyaddingelectrosprayedparticles
electrosprayed particles on top of the PCL fibers. In any case, the performed experiments served to
ontopofthePCLfibers. Inanycase,theperformedexperimentsservedtoselecttheoptimalthermal
select the optimal thermal treatment of 55° for 1 min as the annealing step, in order to retain the
treatmentof55◦ for1minastheannealingstep,inordertoretainthehighestapparentcontactangle
highest apparent contact angle structure that guaranties adhesion to the LDPE layer.
structurethatguarantiesadhesiontotheLDPElayer.

Table1.Apparentwatercontactanglesobtainedforthelow-densitypolyethylene(LDPE)filmandthe
electrospunpoly(ε-caprolactone)(PCL)fibersdepositedfor2hontotheLDPEfilmsthatunderwent
differentthermalpost-treatments.Thevaluesarereportedasmeans±standarddeviations.
Sample ThermalTreatment ApparentWaterContactAngle(◦)
LDPE – 67.3±1.3
LDPE/PCL – 128.5±0.5
LDPE/PCL 55◦for1min 118.5±0.1
LDPE/PCL 55◦for5min 88.3±0.7
LDPE/PCL 65◦for5min 74.2±1.2
LDPE/PCL 70◦for5min 73.1±2.3
LDPE/PCL 80◦for5min 66.6±1.5
LDPE/PCL 90◦for5min 67.1±0.7
Coatings 2018, 8, x FOR PEER REVIEW 7 of 15
Table 1. Apparent water contact angles obtained for the low-density polyethylene (LDPE) film and
the electrospun poly(ε-caprolactone) (PCL) fibers deposited for 2 h onto the LDPE films that
underwent different thermal post-treatments. The values are reported as means ± standard
deviations.
Sample Thermal Treatment Apparent Water Contact Angle (°)
LDPE – 67.3 ± 1.3
LDPE/PCL – 128.5 ± 0.5
LDPE/PCL 55° for 1 min 118.5 ± 0.1
LDPE/PCL 55° for 5 min 88.3 ± 0.7
LDPE/PCL 65° for 5 min 74.2 ± 1.2
LDPE/PCL 70° for 5 min 73.1 ± 2.3
LDPE/PCL 80° for 5 min 66.6 ± 1.5
Coatings2018,8,173 7of15
LDPE/PCL 90° for 5 min 67.1 ± 0.7
33.2.2..D Deeppoossitiitoionno offE ElelcectrtorospsprarayyededS SiOiO2
2
InIn aann aatttteemmpptt ttoo aacchhieievvee suspueprehryhdyrdorpohpohboibci cprporpoeprteiretsi esono tnhet hLeDPLED/PPEC/LP cCoLmpcoosmitpe,o sSitiOe,2
microparticles were electrosprayed onto the LDPE/PCL structure. Once electrosprayed, the
SiO microparticles were electrosprayed onto the LDPE/PCL structure. Once electrosprayed,
2
thmeomrpohroplhogoylo goyf othfet hderdierdie dSiOSi2O papratirctliecsle swwasa schcharaarcatcetreirziezde dbbyy FFEESSEEMM iinn FFiigguurree 44AA.. TThhee loloww
2
concentration used for electrospraying (1 wt %) led to a highly dispersed and distributed coating of
concentrationusedforelectrospraying(1wt%)ledtoahighlydispersedanddistributedcoatingof
the silica, as seen in Figure 4A, obtaining surface aggregates made of nanoparticles with an average
thesilica,asseeninFigure4A,obtainingsurfaceaggregatesmadeofnanoparticleswithanaverage
diameter of approximately 28 nm (Figure 4B).
diameterofapproximately28nm(Figure4B).

FFigiguurere4 .4.( A(A))F Fieiledlde memisissisoionns csacannnniningge leelcetcrtoronnm micircoroscsocoppee( F(FEESSEEMM))i mimaaggeeo offn nananoostsrtuructcutureredds isliilciaca
(S(SiOiO2)2)m micircorpoparatritcilcelsesa fateftreerl eecletrcotrsopsrpayrainygin.g(B. )(BH) isHtoisgtroagmrasmho swhoinwgitnhge tphaer tpicalretiscilzee sdiziset rdibisuttriiobnustioofntsh eof
StihOe2 SniaOn2o npaanrotipclaerstiicnletsh iena tghger eaggagtreesg.ates.
33.3.3..M Moorrpphhoolologgyya annddE Efffefcectto offS SiOiO22E EleleccttrroosspprraayyT Timimeeo onntotoL LDDPPEE/P/PCCLLF Filimlmss
TThheee leelcetcrtorsopsrparyaeydedSi OSi2Om2 imcriocproaprtaicrtleicslewse wreedree pdoespitoesditaetdd aiftf edriefnfetrteimnte tiinmteer vinatlesr(v1a0l–s6 0(1m0–in60) omntion)
thoentLoD tPhEe/ LPDCLPEfi/lPmCsLw fiitlhmasP wCLithd eap oPsCitLio ndetipmoesiotifo2nh t.iImner eolaf ti2o nh.t oInth reetloaptiovnie wtoo tfhteh etoelpe cvtrioewsp roafy ethde
SeiOle2ctlraoyseprsra,iytecda nSibOe2 olabyseerrvs,e idt cthanat bteh eobSsiOer2vmedic trhoapta trhtiec lSeisOw2 merieceroffipcairetnictllyesd wisetrrieb euftfeidcieonnttloy tdhiestsruibrfuatceed
oofnthtoe tehleec sturorsfapcuen oPf CthLe lealyeecrt.roInspTuanb lPeC2,Lo lnaeyecra.n Ino bTsaebrlvee 2t,h oantep caartni colebsaegrgvleo mthearta pteasrtaicclhei eavgegdloammereaatnes
saizcehioefvcead. a1 2m.9eaµnm s.izTeh oisf cmao. 1rp2.h9o µlomg.y Tihsisb emlioervpehdotloogleya ids btoelrieovuegdh tsou lrefaadc etso, reosupgehci saullryfaactetsh, eeshpiegchieasllty
daetp tohsei thioignhteimst edoefp1oshit[i1o8n] .time of 1 h [18].
C oaCtinoagtsi n2g0s1 82,0 81,8 x, 8F, Ox RF OPERE PRE REREV RIEEVWIE W 8 of8 1o5f 15
Table 2. Field emission scanning electron microscope (FESEM) micrographs of the cryofractured
TabTlaeb 2le. F2i.e lFdie eldm iesmsiiosnsi osnca nscnainnngi negle cetlreocntr omni cmroicscroospceo p(FeE (SFEEMSE) Mm)i cmroicgrroagprhasp hosf tohfe t hcrey corfyraocftruarcetudr ed
cross-sections and top views of the nanostructured multilayer films of low-density polyethylene
c(LroDcsPsro-Ess)escc-tsoieoactnteisdo nawns idtah ntodelp et covtprieo wvspiseu wonsfu tolhtfre at thnheai nnnopasnotrloyus(ctεrt-uucrcaetpudrr oemldau cmlttoiunlalety)iel(arPy CfeirLlm )fisfil mboesfr slooafw nldo-dweel-nedsceittnryos siptpyor lapyyoeetldhyeystlihelinycelae ne
((LSiDO(LPDE))mP cEioc)a rctoeopdaat wertdiitc whle iestl.he TcethlreeocstPprCousLnp uduneltp ruaoltsthritaiintoh npinot lipymo(εel-ycw(aεap-scraokplearpcottloacncoteno)sn (tePa)Cn (tLPa)C tfLi2b) ehfri.bs Tearhnsed a SneildOe cetlrenocastnproorsasptyrreuadcy tseuidlri ecsdail ica
2 2
(mSiiOc(rS2oi)Op ma2r)i tcmircoliecpsraowrpteiacrrleetidsc.el epTsoh. seTi thPeedC LPat CddLei fpfdeoerspeitnoitositntiim otinem itnei mtwereav swa lksa,esn pkate mcpoetn lycsot1an0ns,tt2a 0an,tt 3 2a0 ,th 42.0 T,h5h. 0eT, haSnieO dS26 iOn0a2m nnoinasn,traounsctdrtuularcteteudrr, ed
msuibcmrjeoiccptreaodrptitacorletaiscn lwneese arwlein edrgee. pdoespitoesdit eadt daitf fdeirfefnerte tnimt tei minet einrvtearlsv,a nlsa, mnaelmy e1l0y, 1200,, 2300,, 3400,, 4500,, 5a0n, da n6d0 m60i nm, iann, da nd
latelra,t seur,b sjuecbtjeedct teod atnon aenanlienagli.n g.
SiO Layer
CoCatoiCantgoinaTtgiim nTegi mTeim e SiOS2i OL2a2 yLeary er
CCrroCossrsso--sssese-ccsttieioocnnti VoVniei ewVwie w TopTT ooVppi eVVwiiee ww
101m0i n1m0i nm in

20 2m0i nm in

30 3m0i nm in

40 4m0i nm in

50 5m0i nm in

60 6m0i nm in

TheT hper epsreensceen caen da nddi sdtriisbtruitbiounti oonf othf et hSeiO S2i Om2 icmroicpraorptiacrlteisc leosv eorv ethr et heele ectleroctsrpousnp uPnC PLC mL amt wata ws as
furftuhretrh aenr aalnyazleydz ebdy bEyD ESD. TSh. eT hcoem copmarpisaorins oonf Foifg Fuirgeu 5rAe 5,BA f,uBr ftuhretrh reerv reeavleeadl ethda tth tahte t hSieO S2i Om2i cmroicpraorptiacrlteisc les
wewree arrer aarnrgaendg eind tihne t hfoer fmor omf colfu csltuersste, rrsa,n rdaonmdolym dlyis dtriisbturitbeudt eodn otonp t oopf tohfe t helee ectleroctsrpousnp uPnC PLC fiLb efirb leary leary. er.
TheT hhee rhee-oreb-soebrsveerdv ehdie hraierrcahricchali cmali cmroic/rnoa/nnoasntorustcrtuucrteudr esdu rsfuacrfea mceo mrpohroplhooglyo ginyd iincdaticeas ttehsa tth tahte t hcoe actoinagti ng
mamdea doef oufl trualtthrainth iPnC PLC fLib efirbse rasn da nSdi OS2i Om2 icmroicpraorptiacrlteisc ledsi dd indo tn ootn loyn llyea lde atdo ttoh et hfeo rfmoramtioanti oonf oafn an
orgoarngiacn/iinco/irngoarngiacn hicy bhryibdr imd amtearitaelr ibalu tb ualts oal scoo nctornibturitbeudt etdo ttoh et heen heannhcaenmceemnte notf othf et hnea nnoasntorustcrtuucrtaul ral
feafteuarteusr oens othne t hLeD LPDE PfiElm fi.l mTh. iTsh hisie hraierrcahricchalic taolp toogproagprhayp hoyf tohfe t hcoea ctoinagti,n wg,h wichhi cahri saersis ferso fmro tmhe t hmei cmroicnr on
sizesi zoef tohfe t hfieb efirbse arns da nnda nnoamnoemtriect rgica pgsa pams aomngo nthge t hfieb efirbse arss wase wll ealsl aacs raocsrso tshse t hSeiO S2i Om2i cmroicpraorptiacrlteisc liess is
expeexcpteecdt edto toin cirnecarseea steh et hseo lsido–lildiq–uliiqdu idin teinrftaecrfiaacl iaalr eaar eaan da,n dt,h etrheeforerfeo, ret,h et haep paaprpeanrte nstu rsfuacrfea ce
hydhryodprhoopbhiocbitiyc,i tgyi,v ginivgi nrgis er itsoe ato p ao tpeontteianlt isaul pseurpheyrdhryodprhoopbhiocb bice hbaevhiaovr io[1r, 4[1]., 4F]i.g Fuirgeu 5reC 5pCr epsreenstesn tthse t he
EDESD spS escpteructmru, mw,h wichhi cdhe mdeomnsotnrastteras ttehse t hper epsreensceen ocef coafr cbaornb o(Cn )(,C o)x, yogxeyng e(On )(,O n)i,t rnoitgreong e(Nn )(,N a)n, da nsdil isciolinc on
CoatCinogast i2n0g1s8 2, 081, 8x, F8O, xR F POERE RPE REERV RIEEWVI E W 8 of 81 5o f 15
CoatCinogast i2n0g1s8 2, 081, 8x, F8,O xR F POERE PRE REERV RIEEWVI E W 8 of8 1 o5 f 15
CoatCinogast i2n0g1s 82,0 81,8 x, 8F,O xR F POERE PRE REERV RIEEWVI E W 8 of8 1o5f 15
CoatCinogast i2n0g1s 82,0 81,8 x, 8F,O xR F POERE PRE REERV RIEEWVI E W 8 of8 1o5f 15
CoatCinoTgastai n2b0Tgl1sea 8 2b,20 8l.1e ,8 F x,2 i8Fe., Ol xdFR i Fe eOPlmdERE i ePsRsmE iREoiERsnsV RisIoEEcnWaV nIs Enc Wainn gn ienlge cetrleocnt rmonic rmoisccroopsec o(pFeE S(FEEMS)E Mmi)c rmoigcrraopghras pohfs thofe tchrey ocfrryaocftruarcetdu8 roefd8 1 o5f 15
TabTlea b2l.e F 2ie. lFdi eelmd iesmsioisns isocna nsncainngn ienlge cetrleocnt rmonic mroisccroopsceo (pFeE S(FEEMS)E Mm)i cmroigcrraopghrasp ohfs tohfe tchrey ocfrryaocftruarcetdu red
cTraobsTcslre-aos bes2lsc.e -ts iFo2einec. tlsFdi oi aenenlsmdd a iesntmsodipoi s ntsvo iiposec nwav nsise ncwoainnfs gn t ohinefel g et nchetaelrne oncontas rtnomrounisc ctmtrruouirsccecrtdouo psrmeceod u(p FlmetEi luS(aFElytEMielSra E)y fMemilrm) i cfsmri lomoigcfsrr a oloopgwfhr asl-po dowhefns - dstohietfeyn t schpirteoyy lo cypfreryoatolhcyfytreulaterhcnetyduel reende
cTraobscTslre-aos bse2lsc.e- ts iFoe2icne. tlsFid oi aenenlsmdd a iesntmsodipoi s ntsvo ipiosec nwav nisse ncwoainnfs gn to hinefe lg et nhcetaelrn eoncontas rtnomrounisc ctmtrruouirsccectrdouo prsmecedo u(p FlmetEi luS(aFlEytEiMelSra E)y fMemilrm) i cfsmirl omoigcfsrr aoloopgfwhr asl-op dowhefns- dstohietfeny ts chiprteyoy l ocypfreryoatolhcyfyterulaterhcnetyduel e rende
(cTLraoDbscT(PslLrea-EoDs b)se2 Plscc.e- Eots Fia)eo2i tc.nece tolsFdido ai aetnweenlsdmdid t ah iwesnt mesoiditlpoehi s ctn soevt irlpioseoec ncswavt prnissueoc nwnsaoipnn fsu ugn tlon htinref eau lg ettl nhhctertaeilarnn eot ncohpntasior nntomlr oynupis( ccoεtmtrrl-uyouciras(cceεcptrd-ouorcp rosamecelpado ruc(p oFtlmeotlEai nlu(ScaeFltEyt)oEi Men(lSarPeE )yC) fMe mi(LlrPm) )i C cffsmiriLl bomoi)gec fsfrrr i soalb oopgaefwrhnr aslsd-o p da woehnelfsnde- dcst oheitetfrleny eo ts cschiptptrreyoyro a locsypyrfperyoeratdolahcyfy ytserueialtledrhcinec tysduaeli e r liencdea
(cLroDs(cPsLr-EoDs)se Pscc-Eotsia)eo tccnetosdiao atnwensdid t ahw nt eoidtlphe ct eovtrlpieoe cswvtprisuoe wsnop fsu u tlnohtrf eua ttlnhhtraeiann t nhopasionntlr oyups(coεttrl-uyucr(acεept-durc roamelpadruc otlmoltainlucaetlyto)i en(larPe yC)f ei(LlrPm )C ffsiiLl bmo)e ffsr i sbl ooaefwnr sld- oda wenelnde-dcs eitetrlnyeosc sitpptryoroa lsypypeoertdalhyy yseeiltldehinc ysaeli e lincae
((cSLrioDOs(c(PsL2Sr)-EoiD sOms)eP scc2-i)Etocs i)rameo octcneiptocsidaao r otarnwetnpsidic dat lahrw entt sieoidc.tl plhe Te tc sheovt.lrep ieoTe cPswhvtpCreisoue L wsPno pC dfsuu eLtlnopht rf doeu a settlnhithptraeiioano nstnn hoipta isiotnontilrm noypu s(oectεtit rl-muywuc(raceaεept s-duwcr rokaeampledaspru c okttlm lotecainpulocaettnly to)sic enl(toarPaen ynC)fs eti(Ltl rPama )Cn ftfsi tiLl2 bmao) e htffsr i. s2b lo To eahfwhrn .sel d- oT da SwenheilndeO-ed cs 2Seiet tlrinnyeOoasc s2itnpp trnyooor saalsyptnypreoeourtadlshcyty tyresueuiltdrlehcien cytsduaeli e l rinecdae
((SLiDO((PLS2)EiD Om)P 2ci)Eoc )mra otceipocdaar otrwetpidicat lhrwet sieic.tl lheTec shet.lre eoT cPshtpCreou LPsn pC duueLlnpt r douaestlitphtriioanostn hipt iiotnoilm nyp (oetεi l-mywc(aeaεp s-wcr okaaplesapr coktt loecapnocettn o)sc n(toPaennC)s t(tL Paa)nC tf tiL2 ba) e htfr i.s2b T eahhrn.se d T a SehniledOe c S2et ilrnOeoacs2tn prnoorasastnyproeuradscty trsueuidrlcie ctsduai lriecda
m((SLiiDcO((rmPLS2o)EiiDp Ocm)arP 2cor)iEotc pi)marca otclrieeoptcsdiarac otwrlweetpidesicatr lrhwweet sieeidc.tl rlheeTeep cs hetdo.lr eeseTo icpPshttepoCredosu Li Psnta peC dtudu Ledl npt air dftouaf esedlttpihritrefoiianfonsten hitrpt ieitontoiniml nmtyp e(toetεi i lmi-mywnc(eateεae p -sirwcnr vaoktaaeplelsarpsr vco,kt ta lnoeaclpansoc,mtetn on)cse na(otlPaemynn)C s e1t(tL lP0aya),nC t f21 tLi 20b0a) ,,e th f3r 2i.2s0b 0 T,e,a h hr4n3.s0 e0d T, a, Seh5n4il0e0dOe, , c S2ea5t ilrnn0Oeo,dac s2tan pr6nnoor0adsas ntypm r6oeru0iasdnc ty mtr,su euiadirlcnnie cts,ddua ia l rinecdda
ml(m(aSStiiiiecOcOm(m(rrlrSaS2,o2o ))tiiiispp OOeccummarrar2b2oo,rr))i itjtspcp ceiimmurrccaacoolbltrrieiepepttccjsesiidraracc coowr wrlltteetppteoiiessecdaac rrallrrww eeeenttt o siiseedndcc.. rr llaeeeTeeeeTnapp sshhlddno..oi eeneeessTT ippaigPPhthtloeo.eCiCe edndss LLiig PP ttaa ee.CCdd ttdd LLeedd ppaa iiddftftoof feesedsdeppiirriitteffeooiiffoonnsseennititrrtt ee iitttotoinniiimmnnmmtt eettetteii ii mm iimmwnwneetteeaaee iissrrwwnn v vkkttaaaaeeeelsslrrpsps vv,,kktt aa nneecllcppassaoo,,mmtt n n nnccsseeaaoottllammayynnnn ssee11ttttl l 00aayyaa,,nn t t2112 tt 2 20000aa ,,,, th t h322 3..220000 TT,,,, hh h4h334..000 0eeTT,,, , SShh5445ii000ee0OO, , ,, SS22a55a iin00nnnOO,,dada 22aann 66nnnnoo00dadass ntnt mmrr66oouu00iissncnc ttmmttr,r,u u uuaaiirrccnnnneett,,dddduu aa r rnneedddd
lmatiecmlrra,o tispecurrab,or jstpeiucacbltreetjesidc c wltteeosed raw etno end raeeenap lndoineesapigtlo.ei ndsig ta.e td d aift fderifefnetr etnimt eti minete irnvtaelrsv, anlsa,m nealmy e1l0y, 1200,, 2300,, 3400,, 4500,, 5a0n,d a 6n0d m60in m, ainn,d a nd
lmatiecmlrra,o tispecurrab,or sjpteiuaccblrteetjeisdcc wltteeosed raw etno end raeeenap ndloienesapigtlo.ei nsdig ta.e td d aitf fderifefnetr etnimt tei minet eirnvtaelrsv, anlsa,m nealmy e1l0y, 1200,, 2300,, 3400,, 4500,, 5a0n,d a n60d m60in m, ainn,d a nd
latelra, tseurb, sjeucbtejedc tteod a tnon aenanlienagl.i ng. SiOS2i LOa2y Lear yer
Coatinlgaste2lr0a,1 ts8eu,r8,b ,sj1eu7cb3tejedcCC tteoood aaaCC tttnoiioonnn aaaeggnttaii nlTnTniengigiagmm lT.Ti neeiig mm. ee CroCssr-ossesc-tsieocnti VoniSeS VwiiOOi SSe22wii LOOL aa22yy LLeeaarryy eeTrro pT Vopie Vwi ew 8of15
CoaCtoinagti nTgim Tei me CroCssro-ssesc-tsieocnti VonieS VwiOi Se2wi OL a2y Leary eTro pT Vopie Vwi ew
CoaCtoinagti nTgim Tei me CroCsrso-ssesc-stieocnti oVnie SVwiOi Se2wi OL a2 yLeary eTr opT oVpie Vwi ew
CoaCtoinagti nTgim Teim e CroCsrso-ssesc-stieocnti oVnie Vwi ew TopT oVpie Vwi ew
CroCsrso-ssesc-stieocnti oVni eVwi ew TopT oVpi eVwi ew
Table2.Cont.
10 m10in m in
10 m10i nm in
10 m10i nm in SiO2Layer
Coatin1g0 Tm1i0mi nme in
10 m10i nm in Cross-sectionView TopView

202m0i mn20in m in
20 m20i nm in
20 m20i nm in
20 m20i nm in
20 m20i nm in

30 m30in m in
303m0 imn30i nm in
30 m30i nm in
30 m30i nm in
30 m30i nm in

40 m40in m in
40 m40i nm in
404m0i nm40i nm in
40 m40i nm in
40 m40i nm in

50 m50in m in
50 m50i nm in
50 m50i nm in
505m0i nm50i nm in
50 m50i nm in

60 m60in m in
60 m60i nm in
60 m60i nm in
60 m60i nm in
606m0i nm60i nm in

TheT phere psernesceen acne da nddis tdriibsturtibiount ioonf tohfe tShieO S2 iOm2i cmroipcraor ptiaclr etisc loevs eor vtehre tehlee cetlreocstpr o usnp uPnC LP CmLa tm wata sw as
TheT hpere psernesceen acne da nddis tdriisbturitbiount ioonf tohfe thSieO S2 iOm2i cmroipcraorptiacrletisc loevs eorv tehre thelee cetlreocstprousnp uPnC LP CmLa tm wata sw as
furtfhuTerrht haeTen hrpa early enpszaerelenydszc beeeny dac EbneD yda SEnd.Dd Tis Shtd.re iTi sbchtuoreimtb icoupontmai roopinsfa o rtonhifs eo ot fnhS F eioiO gfS 2uF iOrimge2u i 5cmrAreoi ,5BcpAr aforu,pBtria ctfhrlueteriscrt hlroeeevsvr e oerreav vlteeherdea t ltheehdleae ttce httlrhaeoects t tSprhoiueOs npS2 iumPOnCi2 c mLPro CimpcLraa ormtpt iwacalrteat isswc laess
furtfhuTerrthh aeTen rhpa aerly nepszaerelyendszc beeeny dac EbneDy da SEnd.Dd Tis Shtd.re iTi sbchtuoreimt bicouopntmai roopinsfa o rtonhisf eo ot fnhS F eioiO gfS 2uF iOirmge2u i 5crmAreo i,5BcpAr aforu,pBtria ctfhrlueteriscrt h lroeeevsrv e orereav vlteeherdea t ltheehdleae ttce httlrhaeotec st tSprhoiueOs nSp2 iumOPnCi2 c mLPro CimpcLraao rmtpt iawcarlteat isswc laess
wfuerrtfwheu Teeratrrhrh eraeT eana rhnpra aergrlay neepnszdaergel yeindenszcd ebeet nhiyd nace Eb en tfDhy oda er ESn mdf.Dd oTi s Srohtdm.fr e iTics bcolhtuuorfe ismtc bictloeuoupnrtmsasi tro,oep irnsrfaa so rnt,on ihrdsf ae oootn fnmhS dF eioloiO yfgmS 2Fudi Oilrmigyes2u ti d5rcrmAiirebso it,u5cBprArti abeofr,udupBtri ta octferhulndteeri stctroo hl nroepee svt rvo oe orefrpe av t vhltoeeheerfda e tet l htheleheedelca ee tttcelrh ettlorhaecsotctep rst tSorpuhoisuenOps n SpPu2 iumCnOPn LCPi2 c mLCPfrio CbLimcpe Lrfariao brlmtptae iawyrcar letleat arissw.cy leaerss.
wTfwfuuheerrerrttfwfwT hehueuhh eeeeTrraaeerrtrtrrrhrhhee rraaehe eeaaaan-nerrnonrrpara rraabggellraaynnyse-eennoezdazadsggrbelele yyviiedesndnnzzeedd c bbedertt e hiivhyddy nnheee a EE bb idt tnffehhDyyDoo drhee rrESEaS immffdr..DeD oo cTTri rhrSSosoahhmmt..ifrf r eec TTccci a hoocbclhhlluuooffiu eec msmsmcc t accttlileieluuoooppc rrmnmmssarassttor,r,eeipp o ii/rcrrrssnfaaaarssooaorrnn,,tnn iinh/rrddss n aaoooeooooannfsfnnmm nS dtdFF rooiolooliiuOyyfgfgsmm c tFFu 2uddtrlliiurruimyiyggeessrc u u t tedd5i5trrrrcudAiiiAieersbsbr o tts,,eu55uBrrBupdAAiitt bbreafef ,f,usuduudrBBautrr tt c ioottfefercehhuufnnddl aeeerrm tctootrtsroohhe nonrrppo eeeer m tt vrr pvvoooo eroreheffppee r araott vvphoolhllteeeeohhffeedd aag tt oeee lhlh yttleellhoeheeee ddil gcaaceene tttttytllcrdhhr eett otohiaiahccrncsstttoteeapprr d tts ooStSuhhuipescisieennsOOuppa SStntPuuP22eh ii mCnmnCOOsaP LLtPPti22Ci c h c mt mCCffrLrhaiiooLLbbtiiecpc pme e tffrrcahrariioooa bb rrellppattataee iictaayrrycwcio rrlnelelletteaaaarrgiisst.yycsc. i lleeneerrgss..
TwfuhererTwt ehhh eeaeerrrr erhea aa-enonrrarbgela-seynoedzbgre visedneed rdbt vih ynhee Edi tfehDo rheraS imfre.ocrT hraomhirfc cec aholcluif oc mscmatllieu cprmsrasto,rei /cirrnsrasooan, nn/rdnaoooansfmntdFrooluiysgmct udrtluuriyserc tedt5rudiiAsbr tseu,ruBditbre ffsuduaut rcoretefhnda me ctoroeonr pmr et pvooohfepr oat pohlleohfe dgot ehyltloehe ig caentytldre toiichncsteapdrotuSiecsinsapO ttuPehnCsam LttP hit CcfhariLbtoe e tpfchriaob elraae tctiryico nellaaergty.si nerg.
mTwhaeedrTwm ehehe a aeerdorr ehreef a a- eounrorrbeglfat -sernoueadbgrlt tvhiserneedian rdtt vih h nhePei ndti Cfeh oLrhePra imCfrefocriL brhao meriffcc ric ahsbol luief ca mrscanstlliu ed camrs rsntoS,eid ci/rrOnr asoaS,n2 /nridnOmaooan2simn dtcrmoroluoysmictp crdtrlauuyiorsrc pttdetiruacdiislrbr ettseuirsudci tblre desfudasuidt corede fdnan im dctoooe nto p nmr ot opoonothpf lr oyto pohl nhofel leogt yehaly loede lig ec enayttldroed oii c ncstttadhrpooteiu ecs tnsaphf totuPe2ehr nCsmaf otLtPha r tCftamhiiLtboe a et nfcthri iob eoolaea nfctry io naleoaanrgfty. i neargn.
mTwhaeedTmr eheha eedaor hreef r -eaouornbelft -gsroueaebrltdtvhsreeiainrdtnvh hePitndiChe eLrhPa iCreffocriLbhar merifccriahbs loei camrfansl icd caml runoSisdci/tOnr eoSar2 /nsinOm,oa2srin tcamrornuosidctpcrtorauuomrrcptetilaucdyrlr etseidsudc ilr sdesftsauird cirdbe fan uimdcote eto n dmroopnotoh lrnoyopl nhotlloeogyaply odl ieg onaytfdod ii tncthtadhoetei ec tseahf ltoteeehr csmaft ottrha orttmahsitpoe at nucth inooeoa nfctP ionaCoangfLt i nang
omTrhageTmdoa nrhehag ieedcaor /henefi ne-ioucoro/ebflrit -sngroueaoablrtnrtvshrgieeaicanrdt nvh h iehPiycndiC be h rhrLPyiai dCebrf crLirmbhai dreifacc ritahbsme lei rcaamrianstael ild cr am irbnaoSuidlc/i tOnr b oSaa2u/ inlnOtsmo oaa2s in ltccsmroroouosni ctcpcrttrarouuoirncrbptettiuaurcdtirlr beetesidusudc tlr deetsfosdauid c rtde tfhoan imed co te toeh n mnreooph noteha lrnoonyphln choaelloegynmaly codel eegin mnayttddo eioi nnctfttadh o ttie ohec tfsaeh f t otteenhhr smaeaf ot nth anrotmtahasitnoet art notcuhis oocetoatr nfcuut oircnaoaatngftul i rnaangl
omfirbageomdarrneag ildcaoa/enyfi niecuoor/.flrit ngruTaoalthrnthgreiaicant hnh heiPiycnr Cbe h-rLPoyi dCbbf srLimbie derfa vritbmsee edraaritnsahe ldr iaei bnarSudlai tOr b cSau2h iltOsim coa2a i lclcsmroomoni cpcitrcoarorirnbopttiu/arcitrlnbeetaiduscn tledeotodssid t trdt huonied co tt hteun nerooe hnteda lnonyhsn cuaelleyrnmaf cadelecen meattdo emo ntfttoh o rteo hp tfehh f oteohnr lemaofo ngnaroymtasinotiarnontudsi octoirtncfuua rcatoaetnfuls raanl
fomeraagtomfdauerneraag ietdcaous/en firo niecnuoos/f l irt tonhgrunoaeal tr nttLhgrhiaiDcaent n hPL hiPiEcDyn C b fPhirLPElyim Cdb ff rL.ii mlbiT mdefha ri.bmti sTse e rahahritsnaiies eldr arhi banaiSruedlic rtO bh aSaui2rci lctOsamh ola2i i ctlccosmarooplo i ntocpcotrgoarporinrbopattiupgarcirrthlbeateyiudspc to lheedtfyods it d hotdt fehoin tde chot o hteena nectoo hiontne aanlgonyth,in c nwalelgeynmha, c idwleecenm hhatt doie aco nrhttiftsho aeto erhst fi he sfft oerehnosr e mamffo nrna rootmtahmsinoeta ro nttmuhsi octeoirtnc fuumr rcoaoiatnncful r raoannl
fotehragatfoauternragtiehtcause/n rionieccnsoo/ irtoanhgtnoeai nr ntLghgiDcae mn PLhiEDcay d bPfhierElyimdb of ri.f lmiTmduha l.mtt iTsera rhahittiaihesel ir rhnibaairuelPc rtbhCa auirLccltsah ofilai ctlbcosaeooplr ntoscotgorparinnobatdguprirthbeaSyudpi Oto hetfyod t ohmttfeho i te ccht roheeoa nepct hioaneaarngtntihi,cc nwaelgenmh,sc iweecdnmhhit die aconrhnifts oaetorthsfi es oft ernhnosle amyf rnno oltaemhsanet rdo tmuhsctteiortc uumrtrcohiatncuelr roanl
sfoeirzagetfosau eironzargfieet acu st/noh rioinfeec ns ot/f hirtoinhbgeno eea frr tniLghsbi Daceea n rnLPhsidEDc ya bPnfhnirEdyalimdnb fn roi.l maimTmdnha eo.m titTmesr rhaihecitiai tesegrl r rihaicbaaip urelgs crta bha apaurimccsltsah ooalai nm cltscoagooolp tnntohcotggoerp rin tobafhtiguprbeirth ebaefyruidpsb toh eeatfy2rods st oh wttafeho set e chlwt lohe eaae enctsl hiol en aaaangctnshir, cn owaaegsncmhs,rc owieetcshmnhhset ie a tcSonhrhiifteO s a etoSr2hs fii mes Ofte rh2inso ce mamfr rnonoi potcamhrsanoetr rot ptmuhisacctelirrt ectumuirsccro iliatcnesulr s ro ainsl
sffeiozaretsfmu eiozarafeet tu stioho rofeen ns tfh otoihbefn eeaf r tinLhsb Deeoa rrnLPsgd EDaa nPnfniiEdalcmn /fnoi.il anmTmnoheo.r itTmgsr ahihecniit seirg cirhacahip regyscra hbaaprirmccsida hoali mnmctoagoalp tnttoehoggrep ir taoafhligpbebrh eaufyriptsb oh eaafyrls sst ooh wafe scet ochlwlone aaet crtslioil nb aaaguctsir,t n oeawgdschs,r otwitocshhhste iha tcSherhiieO sea enSr2s iih mOsfaer2niso c mcmfreroio mpctmhraeoer npt tmhtiaceorli ectfmirscto hilicnesers o ins
esfeixzapetsfeeu eixoczarptfeete eu stdoch ro ftee enst tdfh ooti e hbn eetif ontr iLhbs c Deerai renLnPsac DdEsrae ePnfn aiEdalsmt nehfn io.ela mmT tnhhsoe.e oitTms rl hiihsedcioti s–ergl lihiraicdaqip er–guscrlai ihadqaprimu ccsa hiioadlni mnc ttaoegoilprn ntftothaogegcep rrit foaafhaiglpecb rih eaafayriplrbs eho eaaafyr s rs t eo hawaafen s et dchlwaol,e naae cdttlsoihl ,n aaeagctrstir,eh n oawfegocsrh,srre o ewiftc,soh hhsre ieta tch,Shrh eiie Os ta heSr2ase iipO ms fepr2aiso ac pmmfrrrpeoio ncaptmhrtra oeer npt tsmhituac erilr ectfsmirasuco cilricenesfrs a o cines
esnixzapensee ixooczpstfeet e rtdochu tfece t ttdfhoui e br ateifolnrib sfce eriaarennstacu dsrare enen adsast neohn oneam tnthhsoeeoetm rlLiisedcDot –rglPliiaicdEqp –gusfilaii qldapmmu s i.ioadnTmn thegioirn sntfthahgecer iiet fafharilaceb ir eafacrilrhbs e ieaacara srs el awaatnos e dplwal,o n aegdtlsrhl, a aeapcrtshrhe oafyeocsrsroreo efft,osht srhe ete th,Sh ecieOo t hSa2ae tipOmi np2aig acpm,rrpweoinacphrrta oiercnptshituac arlretrfsiaisucs clreieesfss a cies
hesixyzpdeseher ixyoczoptdfepe e rthdochootf pee bt tdhhfiocio e bibt tefiyoinric,b s ic gteriayrnienv,sac digsranee ingnva d iasrnt enhing soeae mt rn hitsoseoeoemt r altiise docpot –rgloaiilac dtiqpe p–gnuoslatiit qidapeaunm sl itisadoinaumn tlp geiosenr untfrthaphgecer yeit fradhfahilrceb yoi eafdaprilrrbhs eo eoaaaprb srshe i awcoaa nsb be dilewacl,hn eabadltsevlh, h aiaeoactsrrvhre aoife[oocs1rrrsre,4o ef[t]os,1h. s r,eF 4ett hi],hS g.e ieuFO t hriS2ageei pOu m 5pr2aCie acpm rr5ppeoiCrnacper rtapsoe renprtsneitauc strlsretesf niatsucht clrsieeesf s a t hciees
hefxryopdhemerxycopdttpeherhdcoeot pembthdioico c ibrttiyoionc,n ictgriysnieiv,az cigsreneeivgoa i fsnrtethig hse eet r hitfissoeeob aletis odrpos –laoial dtinpqe–nduoltitiqnideanua l ntiisdinoau lmtp eisenreufrttaphercireycifradahglrc yaoiapdaplrsrh eooaaapmb rheiacooa nnb bdigeac,h n tbhadteveh,h iefioatrrvbhe iefe[oo1rrrsre,4 ef[a]o,1. s r,F4etwh]i, g.ee uFl tlhirgaaeepu s 5praaCeacp rr5ppeoCrnase rstpse tenrhsnetues tsreSsf natuihtOcrseef a thcee
EhexDypdSheEerx yDscopdptpSeereh dcoscot ptperbehtduiococ mt ibrttu,iyio ncwm, i ctghriy,n ieiw,vca cgihrshneie ivdga ci eshnrtem higd se oeetr nmhitsssoeeoot r nlatais osdtopt e–rlaosila d titptqee–hnousleitti qteidpahnu rlet iedi ispsnau elrtp neeisnerscufreetaphen coreyciffraeda hc lcro ayoifradap blcrr hoaoeornaapbbr h(oeiCoacan nb) b,(di Ceaco,h nx )b,ady teovhg,h xieeoaytnrvrheg i(ef[eoOo1rnrer,) 4 ef,([ ]oO,1n. r ,i)4Fett,]hr, in .go eiFugt thirregaoeenup g 5(rpeaNCenap )r 5pp(,e CNaarne nr)tpse ,d enra snesntus itdlserisf ncsatuothicrslneeif 2ca t ohcnee
EhmDyidScEhrr yDsoodpppSre haoscorptptrbeihucicoclmteibrtsu,yi cwmi,i stgh,ye iiw,vxc gihphni eivdgcci hetnrem igdds oeert mnitossoeoti r nnata osctptr eraeosaa ttptesehnoesett tteiphhanrleet e ispssaueolrp nelsiescuderep–hn oleycifrqed hc uroayoifrddp bcrhaoionornpbtb eh(oiCrocnf b)a b,(ic Cecoih ax)b,aly eovaghxireoayenvrag i(e[oaO1nrn,) 4d(,[ ]O1n,. ,i)4tFt,h] rin.geo iFrugteirregfoenou g r5(reeNCen, ) 5tp(,h NCaree n)ps,ad erap nenspsitdlseai nrcsteotihlsnnie ct tohne
EhDydEhSr yDsodppSre hoscopptrbehuicocmtibrtu,iy cwm,i tgh,y iwi,vc gihhni ivdgcih enrm igds oeerm nitssoeot rnataos tpt eraosa t tpteehonset t teiphanrlet e ispasuelr penssecuerephn oeycfred hc royaofrd pbcrhaooronpbb h(oiCocn b) b,(i Ceco hx)b,ay eovghxieaoynvrg i(e[oO1nr,) 4(,[ O]1n. ,)i4Ft,] rin.go iFugtirregoenug 5(reNCen )5(p,NC are n)p,sd era ennssitdlesi ncstotihlsnie ct ohne
EsuDrES fa DscpSee shcptyreducrmtorpu, hwmoh,b wiicchhit iydc,hegm divoeimnnsgotrnraisstteersat ottehase p tphorete epsnerteniascelens oucfep c eoarfrh bcyaodrnbr o(oCpnh) ,(o Cobx)i,cy ogbxeeynhg a(eOvni) o(, rOn[)i1t, r,n4oi]gt.reFonigg (euNnr )e(,N 5aCn),d pa nsreidlsi ecsnoilntisc on
ED ES DspSe scptreucmtru, mwh, wichh idchem deomnsotrnasttersa ttehse t phree pserensceen ocfe coafr cbaornb o(Cn) (, Co)x,y ogxeyng (eOn )(,O n)i,t rnoigtreong (eNn )(,N an),d a nsidli csoilnic on
the EDSspectrum,whichdemonstratesthepresenceofcarbon(C),oxygen(O),nitrogen(N),andsilicon

(Si) , characteristic elements of the electrospun fibers and the electrosprayed particles. In addition,
thepeakintensitieswereproportionaltotheweightcontentofeachelementonthesamplesurface[24].
Furthermore,theappearanceoftheSipeakconfirmedthepresenceoftheSiO microparticlesonthe
2
electrospunPCLmembranesurface,asexpected.
Coatings 2018, 8, x FOR PEER REVIEW 9 of 15
(Si), characteristic elements of the electrospun fibers and the electrosprayed particles. In addition, the
peak intensities were proportional to the weight content of each element on the sample surface [24].
CFouatritnhgse2r0m18o,r8e,,1 7th3e appearance of the Si peak confirmed the presence of the SiO2 microparticles o9no tfh15e
electrospun PCL membrane surface, as expected.

FFiigguurree 55.. ((AA)) FFiieelldd eemmiissssiioonn ssccaannnniinngg eelleeccttrroonn mmiiccrroossccooppee ((FFEESSEEMM)) mmiiccrrooggrraapphhss sshhoowwiinngg aa ttoopp--vviieeww
iimmaaggee ooff tthhee eelleeccttrroossppuunn uullttrraatthhiinn ppoollyy((εε--ccaapprroollaaccttoonnee)) ((PPCCLL)) fifibbeerrss ccooaatteedd wwiitthh eelleeccttrroosspprraayyeedd ssiilliiccaa
((SSiiOO22)) mmiiccrrooppaarrttiicclleess;; ((BB)) FFEESSEEMM mmicicroroggrarapphhs srerpepoortretded ini n(A(A) b)ubtu ptrporcoecsesessde bdyb eyneenrgeyrg-dyi-sdpiesprseirvsei vXe-
Xra-rya sypsepcetrcotrsocsocpoyp y(E(DESD)S; )(;C()C E)DEDS Smmicricoraonaanlaylsyiss isspsepcetcrturmum. .
33..44.. SSuurrffaaccee WWeettttaabbiilliittyy ooff IInnccrreeaassiinngg SSiiOO22 EElleeccttrroosspprraayyiinngg TTiimmee oovveerr LLDDPPEE//PPCCLL
FFiigguurree 66 sshhoowwss tthhee eevvoolluuttiioonn ooff tthhee aappppaarreenntt wwaatteerr ccoonnttaacctt aannggllee vvaalluueess aatt ddiiffffeerreenntt pprroocceessssiinngg
ttiimmeess ffoorr tthhee mmuullttiillaayyeerrL LDDPPEE//PPCCLL//SSiiOO22 ffiilmlm. .TThhee vvaalluuee ooff tthhee aappppaarreenntt wwaatteerr ccoonnttaacctt aannggllee ffoorr tthhee
nnoonn--ccooaatteeddL LDDPPEEfi lfmilmw awsa6s7 .36◦7.a3n° datnhdis tihnicsr eianscerdeatose1d1 8t.o5 ◦1w18h.e5n° cwohateend cwoiathtePdC wLifithb ePrsC(Lse feibperersv i(osuese
Tparbelveio1)u.sF rToamblteh 1e)r.e F,trhoema pthpearree,n tthwe aatpepracroenntat cwtaantegrl ecovnatlaucets apnrgolger evsasliuveesly pirnocgrereassseidvwelyit hinacnreinascereda sweiitnh
tahne eilneccrteroasspe rainy intghet imeleecotfrSoisOp2ratyoinagv atliumeein oefx cSeisOs2o ft1o5 0a◦ ,vsualpupeo ritnin gexacseussp eorhf y1d5r0o°p, hsoubpicpboerhtianvgi ora.
supeIrthycdanropbheobhiycp boethhaevsiizoer.d that at deposition times lower than 50 min, the electrosprayed
SiO2Imt cicarno pbaer thicylpesotlhaergsiezleydfi tlhleadt atht edevpooidsistiaomn otinmgetsh eloewleecr trtohsapnu 5n0 PmCiLn,fi tbheer seliencsttreoasdproafyesdea StiinOg2
hmoimcroogpeanrteiocluessl ylaorvgeerlyt hfeillueldt ratthhei nvfiobidesr laamyeorn.g Fothrea eslielcictarodspeupno siPtiConL tfiimbeerso fin1shte,atdh eoaf pspeaarteinngt
whoamteorgceonnetoauctslayn ogvleerw thase uselternatthoinr efaibcehr alavyearlu. Feoorf a1 s5i7li.c4a◦ d±ep0o.1s◦it.ioTnh itsimpea rotfi c1u hla, rthsea mapppleareexnht iwbiatetedr
acosnlitdaicnt ganagnlgel ewoafs 8se◦e.nT htois rseuacghg eas tvsatlhuaet ,off o1r57th.4i°s ±p r0o.1c°e.s sTihnigs tpimareti,cuthlaer asmamoupnlet eoxfhnibaintoedst rau scltiudriendg
SainOg2lem oicfr o8p°.a rTtihcilse sseuxgcgeeesdtes dtthhaet,t hforers hthoilsd vparoluceesrseiqnug irteidmteo, ctohve eramthoeuPnCt Lofif bnearnsousrtfrauccetuarnedd, tShiuOs2,
gmeincerroaptaerdtitchlees neexcceesesdareyd stuhref atcheretoshpoolldo gvyatlouea trteaqinuisruepde troh ycdorvoeprh tohbei cPitCy.LA flisboe,r ssinucrefatchee ainndor, gtahnuisc,
ngaennoesrtartuecdt utrheed nmecicersospaaryrt isculersfawcee rteoipnoselortgeyd tion aatdtaeinns esulapyeerrhoyfdPrCoLphfiobbeircsi,tays. sAhloswo,n siinncTea bthlee2 i,nitocragnanbiec
hnyapnootshtreusiczteudretdh amttichreoapsapretircilteiess wbeertwe einesnetrhteede lienc tar odsepnusne filabyeerrs oanf dPCthLe feibleecrtsr,o asps rsahyoewdnm iinc rTopabalreti c2l,e ist
ecnanh abnec ehdytphoetshuersfiazeced rtohuagt htnhees saospfethrieticeos abteedtwseuebns trtahtee e[4le].ctArocscpourdni nfgibteorst haenCd atshsiee –eBleacxttreorspmroadyeedl,
amnicinrocrpeaarsteicilness uenrfhaacnecreodu gthhen seussrfaancde reonutrgahpnpeesds oaifr tchaen cloeaatdedto suabrsetdruatcet i[o4n]. iAncthcoerrdaitniog otof tthhee wCeatstsinieg–
pBhaaxsteert omtohdeenl,o ann- winectrteinagsep ihna ssuer[f1a,c2e5 r],oluegahdninegsst oanwda etenrtrraepppeellde nacire .cIann tlheiasdr etog aar rde,dfuurctthioenr ainn athlyes risatoiof
tohfe tchoen wtacetttainngg lephmaesaes utor etmhee nntosnin-wteertmtinsgo fphhyasstee r[e1s,i2s5a],n ldeasdtaibnigli ttyo owftahteerC raespseiellwenecteti.n Ign stthatise [r2e6g–a3r0d],
cfouurtlhdepr raonvaildyesiasd odfi ttihoen acolnvtaalucta abnlegilne fmoremasautiroenmaenndtsw inil ltebremths eosf uhbyjsetcetroefsifsu artnhde rstwaboirlkit.y of the Cassie
wetting state [26–30] could provide additional valuable information and will be the subject of further
work.
Coatings2018,8,173 10of15
Coatings 2018, 8, x FOR PEER REVIEW 10 of 15

FFiigguurree 66.. AAppppaarreenntt wwaatteerr ccoonnttaacctt aannggllee ooff tthhee mmuullttiillaayyeerr ffiillmm bbaasseedd oonn llooww--ddeennssiittyy ppoollyyeetthhyylleennee
((LLDDPPEE)),, poployl(yε(-εca-cparporlaoclatocntoen)e(P) CL(P)CfiLb)e rsf,iabnedrss, iliacand(S iOsi2l)icma icr(oSpiOar2)ti clmesicfororpdaifrfteicrelenst elfeocrt rodspifrfaeyreinngt
edleepctorsoitsipornaytiimnges d(e1p0,o2s0it,io30n, 4ti0m,5e0s ,(a1n0d, 2600, m30in, )4o0f, S5i0O, 2a.nTdh e60p rmofiinle) soof fStihOe2w. Tahteer pdrroofpilleetss oafr ethinec wluadteedr
dasroinpsleettss aforer einacclhutdimede apso iinnste.tTs hfoere eleaccthro tsimpuen pPoCinLt. dTehpeo eslieticotnrotsipmuenw PaCsL2 dhe,paonsdittihoen tthimerem walatsr 2ea htm, aenndt
twhaes thcaerrrmieadl toruetatamt5e5nt◦ Cwafos rca1rmrieind. out at 55 °C for 1 min.
33..55.. EEffffeecctt ooff tthhee EElleeccttrroossppuunn PPCCLL DDeeppoossiittiioonn TTiimmee oonn SSuurrffaaccee WWeettttaabbiilliittyy
IInn oorrddeerr ttoo aasssseessss tthheep pootetenntitaialle feffefcetcto fotfh teheP CPLCLth tihckicnkensesslsa ylaeyreorn otnh ethaep paparpeanrtecnotn ctoancttaacntg alengfoler
ftohre tghiev egnivoepnt iompatilmSiaOl 2SicOoa2 tcionagtitnimg etiomfe1 ohf, 1d ihff,e dreifnfetreelenctt erolescptirnonspinignndienpgo dsietpioonsittiimone stiomfeths eoPf CthLe lPayCeLr
lwayereer iwnveerset iignavteesdt.igTaatbelde. 3Tgaabtlhee r3s gthaethFeErsS EtMhe imFEaSgEeMso fimthaegLesD PofE tfihlem LsDcoPaEte dfilwmist hcothaeteedle cwtritohs ptuhne
ePlCecLtrfiobseprusna tPdCiLff efribenertsp arot cdeisffseinregntti mpreosc,ersasnignign gtimfroems, r1a0ntgoin6g0 fmroinm, a1n0d toto 6p0 cmoainte, danwdi tthopth ceooaptetidm wiziethd
tehleec otrpotsimpriazyeidn geleticmtreosopfrtahyeinSgiO ti2mnea noof stthreu SctiuOr2e ndamnoicsrtroupcatrutricelde smoifcr6o0pmaritnic,lfeosl loofw 6e0d mbiyn,a fnolalnowneeadli nbyg
atrne aatnmneenatl.inFgr otmreactlmoseenitn. sFpreocmti ocnloosfe thinespcreocstsio-sne cotfi otnheim craogsess-,sietcitsioens tiimmaagteeds, tihta itst hesetitmhiactkende sthsaotf tthhee
tehleiccktrnoesspsu onf tPhCe Lelceocatrtoinsgpsunin PcrCeLas ceodatfirnogms icnac.r3eaµsmed, ffroormth ceafi. 3lm µmsa,m foprl ethsew fiiltmh 1s0ammpinleos fwdiethp o1s0i tmioinn,
oufp dteopcoas.it1i7onµ,m upfo trot hcae. fi1b7e µrsmp froorc ethssee fdibfeorrs6 p0rmociens.sTeadb floer2 6s0h mowins. tThaabtlteh 2e sehleocwtrso stphautn thPeC eLleccotartoesdpfuonr
P2ChLp croeasetendte fdora 2t hh ipckrenseesnsteodf caa t.h4ic0kµnmes,s ionfc clua.d 4i0n gµmth,e inSciOlu2dlianyge trheel SeciOtr2o lsapyreary eeldecftorors6p0ramyeind. for 60 min.
FFoorr aallll pprroocceessssiinngg ttiimmeess,, tthhee PPCCLL ffiibbeerrss ssttrroonnggllyy aaddhheerreedd ttoo tthhee ssuubbssttrraattee,, aann eeffffeecctt tthhaatt iiss,, aaggaaiinn,,
aassccrriibbeedd ttoo tthhee tthheerrmmaall ppoosstt--ttrreeaattmmeenntt.. TThhee ttoopp--vviieeww ppiiccttuurreess ooff TTaabbllee 33 ((iinn ccoommppaarriissoonn wwiitthh pprreevviioouuss
TTaabbllee 22)) ssuuggggeesstt ththaat tloloww PCPCL Ldedpeopsoitsiiotnio tnimtiems easftaefrt aenrnaenanlienagli ndgo ndoot nseoetmse teom crteoatcer eaa stuebastsruatbes wtraitthe
ewniothugehn ofuibgehrsfi fboerr sthfoe rStihOe2 SmiOic2rompiacrrtoipclaerst itcole gsetnoegraentee rtahtee ctohnetcinounotiunsu ovuosidveodi dtoedpotloopgoyl orgeyqureirqeudi rfeodr
sfourpseurhpyedrhryodprhoopbhicoibtyic. it y.
TTaabbllee 44 ggaatthheerrss tthhee aappppaarreenntt ccoonnttaacctt aannggllee ooff tthhee fifillmmss aafftteerr ccooaattiinngg wwiitthh iinnccrreeaassiinngg ddeeppoossiittiioonn
ttiimmeess ooff PPCCLL, ,rarnangigning gfrformom 101 t0o t1o201 2m0inm, ainn,da 6n0d m6i0n mofi neleocftreolespctrraoysipnrga oyfi nSgiOo2f mSiicOro2pmarictircolpesa.r Ttihculess,.
fTohru asn, efolercatrnosepleinctnrionsgp idnenpionsgitdioenp toismiteio onf 1ti0m meinof, t1h0e mapinp,arthenet acpopnatarectn atncgolnet vacatluaen rgelaecvhaeldu ea vreaaluche eodf
9a8v.8a°l uaendo fth98u.s8,◦ waansd ctlheaursl,yw naost cslueparelryhyndortospuhpoebrihcy. dTrhoep huoseb iocf. Tlohneguers eeloefctlroonsgpeurne PleCctLr odseppuonsiPtiConL
tdimepeoss fiutirotnhetri minecsrefausretdh ethrei nacprpeaarseendt wthaetearp cpoanrteanctt awnagtleer vcaolunetas,c ptearnhgalpesv daulue etos, thpee rphraepsesndcue eoft mo othree
fpirbersoeunsc estorufcmtuorreesfi, bleraoduisnsgt rtuoc teunrheas,nlceeadd irnogutgohennehssa nacnedd aro ruegdhuncetisosna nind paorreodsuitcyti o[3n1i]n apnodr osshiotyw[i3n1g]
vanalduessh oawboivneg 1v3a0lu°.e Hs aobwoevveer1,3 a0s◦ .eHxpolwaienveedr ,aabsoveex,p olanilnye d12a0b movien, oofn PlyC1L2 0dempoinsitoifonP CgLendeeraptoesdi titohne
rgeeqnueirraetde dmtohreprheoqluoigreyd tom aocrhpihevoelo sguypteorhaychdireovpehsoubpiceirthyy. drophobicity.