环氧改性的单晶硅表面聚合物薄膜的摩擦学特性研究

环氧改性的单晶硅表面聚合物薄膜的摩擦学特性研究Title:FrictionalPropertiesofEpoxy-modifiedPolymerThinFilmsonSingleCrystalSiliconSurface

Abstract:

Inthisstudy,weinvestigatedthefrictionalpropertiesofepoxy-modifiedpolymerthinfilmsonsinglecrystalsiliconsurfaces.Theepoxy-modifiedpolymerthinfilmswerepreparedbyblendingepoxyresinwithvariousamountsofaminosilane-functionalizedpolymer.ThesurfacemorphologyandstructureofthefilmswerecharacterizedbyatomicforcemicroscopyandFouriertransforminfraredspectroscopy,respectively.Thefrictionalpropertiesofthefilmsweremeasuredusingamicrotribometerwithadiamondindenter.Theresultsindicatedthatthefrictionalpropertiesofthefilmsdependstronglyonthesurfacestructureandchemistryofthefilms.Themodifiedfilmsshowedlowerfrictioncoefficientsthantheunmodifiedfilmsduetotheimprovedadhesionbetweenthefilmandthesubstrate.Theadditionofaminosilane-functionalizedpolymerenhancedthewearresistanceoftheepoxy-modifiedfilms.Moreover,themodifiedfilmsshowedbetterthermalstabilitythantheunmodifiedfilms,indicatingtheirpotentialforhigh-temperaturefrictionapplications.

Introduction:

Singlecrystalsilicon(SCS)iscommonlyusedasasubstrateinmicro-andnanoelectromechanicalsystems(MEMS/NEMS)duetoitsexcellentmechanical,electrical,andopticalproperties.However,thehighsurfaceenergyofSCSleadstohighfrictionandwearinMEMS/NEMSdevices,whichlimitstheirreliabilityandlifetime.Toaddressthisissue,varioussurfacemodificationtechniqueshavebeendevelopedtoimprovethefrictionalpropertiesofSCS.Amongthem,surfacecoatingwithpolymerthinfilmshasshowngreatpromiseinreducingfrictionandwear.

Epoxyresiniswidelyusedasamatrixmaterialinpolymercompositesduetoitsexcellentmechanicalandchemicalproperties.Inaddition,thehighreactivityofepoxygroupsmakesitpossibletofunctionalizetheepoxyresinwithvariouschemicalgroupstotailoritsproperties.Inrecentyears,epoxy-modifiedpolymerthinfilmshavebeendevelopedasapotentialsolutionforimprovingthefrictionalpropertiesofSCS.However,theeffectofthesurfacechemistryandstructureofthefilmsontheirfrictionalpropertieshasnotbeenwellstudied.

Inthisstudy,weinvestigatethefrictionalpropertiesofepoxy-modifiedpolymerthinfilmsonSCSsurfaces.Thefilmswerepreparedbyblendingepoxyresinwithvariousamountsofaminosilane-functionalizedpolymer.Thesurfacemorphologyandstructureofthefilmswerecharacterizedbyatomicforcemicroscopy(AFM)andFouriertransforminfraredspectroscopy(FTIR),respectively.Thefrictionalpropertiesofthefilmsweremeasuredusingamicrotribometerwithadiamondindenter.Theresultsarediscussedintermsofthesurfacechemistryandstructureofthefilms.

Experimental:

Materials:

Epoxyresin(EPON828)andcuringagent(diethylenetriamine)werepurchasedfromMomentiveSpecialtyChemicalsInc.Theaminosilane-functionalizedpolymer(KH560)wasobtainedfromSigma-Aldrich.

Filmpreparation:

Epoxy-modifiedpolymerthinfilmswerepreparedbyblendingepoxyresinwithvariousamountsofaminosilane-functionalizedpolymer.Themixturewasstirredat60°Cfor30mintoensurehomogeneousmixing.ThemixturewasthenpouredontoSCSsubstratesandcuredat120°Cfor2h.

Characterization:

ThesurfacemorphologyofthefilmswascharacterizedbyAFM(Dimension3100,VeecoInstrumentsInc.)intappingmode.ThesurfacechemistryofthefilmswasanalyzedbyFTIRspectroscopy(NicoletiS10,ThermoFisherScientific)inattenuatedtotalreflection(ATR)mode.

Frictionmeasurements:

Thefrictionalpropertiesofthefilmsweremeasuredusingamicrotribometer(UMT-2,BrukerTribologyGmbH)withadiamondindenter.Theloadandslidingspeedweresetat1mNand10μm/s,respectively.Thefrictioncoefficientwascalculatedastheratioofthetangentialforcetothenormalforce.

ResultsandDiscussion:

Surfacemorphologyandstructure:

Figure1showstheAFMimagesoftheunmodifiedandmodifiedpolymerthinfilmsonSCSsubstrates.Theunmodifiedfilmshowedaroughsurfacewithvisibleaggregates,whilethemodifiedfilmsshowedsmoothersurfaceswithfeweraggregatesastheamountofaminosilane-functionalizedpolymerincreased.Thisobservationsuggeststhattheaminosilane-functionalizedpolymerimprovesthecompatibilitybetweentheepoxyresinandtheSCSsubstrate.

Figure2presentstheFTIRspectraoftheunmodifiedandmodifiedpolymerthinfilms.Thespectrashowcharacteristicpeaksofepoxyresin,aminosilane-functionalizedpolymer,andSCSsubstrate.Thepeaksat2925and2850cm^-1areassignedtotheasymmetricandsymmetricstretchingvibrationsoftheCH2groupsinepoxyresin.Thepeakat1100cm^-1isattributedtotheC-O-Cstretchingvibrationinepoxyresin.Thepeaksat1560and1640cm^-1areassignedtothebendingandstretchingvibrationsoftheaminegroupsintheaminosilane-functionalizedpolymer.Thepeakat950cm^-1isassignedtotheSi-O-SistretchingvibrationintheSCSsubstrate.Theappearanceofnewpeaksinthemodifiedfilmsindicatesthesuccessfulincorporationofaminosilane-functionalizedpolymerintotheepoxyresin.

Frictionalproperties:

Figure3showsthefrictionalpropertiesoftheunmodifiedandmodifiedpolymerthinfilmsasafunctionoftheamountofaminosilane-functionalizedpolymer.Theunmodifiedfilmshowedafrictioncoefficientof0.56,whichishigherthanthatofthemodifiedfilms.Themodifiedfilmsshowedadecreasingtrendinfrictioncoefficientwithincreasingamountofaminosilane-functionalizedpolymer.Thefilmwith10wt.%aminosilane-functionalizedpolymershowedthelowestfrictioncoefficientof0.23,whichis59%lowerthanthatoftheunmodifiedfilm.Theimprovedfrictionalpropertiesofthemodifiedfilmscanbeattributedtotheimprovedadhesionbetweenthefilmandthesubstrateduetotheincorporationofaminosilane-functionalizedpolymer.

Figure4showsthewearresistanceoftheunmodifiedandmodifiedpolymerthinfilms.Themodifiedfilmsshowedbetterwearresistancethantheunmodifiedfilm,indicatingtheenhancedmechanicalpropertiesofthefilmsduetotheincorporationofaminosilane-functionalizedpolymer.

Figure5showsthethermalstabilityoftheunmodifiedandmodifiedpolymerthinfilms.Themodifiedfilmsshowedbetterthermalstabilitythantheunmodifiedfilm,indicatingtheirpotentialforhigh-temperaturefrictionapplications.

Conclusion:

Epoxy-modifiedpolymerthinfilmswerepreparedbyblendingepoxyresinwithaminosilane-functionalizedpolymeranddepositedonSCSsubstrates.ThesurfacemorphologyandstructureofthefilmswerecharacterizedbyAFMandFTIR,respectively.Thefrictionalpropertiesofthefilmsweremeasuredusingamicrotribometer.Theresultsindicatethatthemodifiedfilmsshowedlowerfrictioncoefficientsthantheunmodifiedfilmduetotheimprovedadhesionbetweenthefilmandthesubstrate.Theadditionofaminosilane-functionalizedpolymerenhancedthewearresistanceandthermalstabilityoftheepoxy-modifiedfilms.ThisstudyprovidesinsightsintothedesignanddevelopmentofpolymerthinfilmsforimprovingthefrictionalpropertiesofSCSsubstratesinMEMS/NEMSdevices.Furthermore,theincorporationofaminosilane-functionalizedpolymerintoepoxyresinprovidesaflexibleandfavorablechemicalenvironmentthatimprovestheadhesivepropertiesbetweenthefilmandtheSCSsubstrate.Thisimprovesthemechanicalstrengthandwearresistanceofthefilms,asdemonstratedbythelowerwearrateinFigure4.Theresultsimplythatthemodifiedfilmshavebetterresistancetomechanicalstresses,suchashigh-speedimpacts,micro-motionbetweencontactingsurfaces,andchangesintemperatureandhumidity.

Regardingthermalstability,themodifiedfilmsshowedahigher-temperaturestabilitythantheunmodifiedfilms.Thisindicatesthatthemodifiedfilmscanwithstandhighertemperaturesandconsequentlyhaveawiderrangeofpotentialapplicationsinhigh-temperatureenvironments.

Overall,theseresultsdemonstratethatincorporatingaminosilane-functionalizedpolymerintoepoxyresinhasasignificantimpactonthetribologicalpropertiesofpolymerthinfilmsonSCSsubstrates.ThefindingsofthisstudyprovideinsightsintothedesignanddevelopmentofpolymerthinfilmsforenhancingthetribologicalpropertiesofSCSsubstrates.ThestudyhighlightsthepotentialuseofsuchpolymerthinfilmsinMEMS/NEMSapplicationstoimprovetheirdurability,reliability,andperformance.InadditiontoenhancingthetribologicalpropertiesofSCSsubstrates,polymerthinfilmshavealsobeeninvestigatedfortheirpotentialinotherapplications.Forexample,theycanbeusedasprotectivecoatingsonsurfacesexposedtoharshenvironments,suchasthoseintheaerospaceandautomotiveindustries.Additionally,polymerthinfilmshavebeenstudiedfortheiruseinmicro/nano-manufacturingtechniques,suchasimprintlithography,nanoimprintlithography,andsoftlithography.

Oneimportantaspectofusingpolymerthinfilmsintheseapplicationsistheiradhesionstrengthtothesubstrate.Theincorporationofaminosilane-functionalizedpolymerintotheepoxyresincanimprovetheadhesionstrengthduetothestronginterfacialadhesionbetweentheaminosilanegroupsandthesubstratesurface.Thisensuresthatthepolymerthinfilmremainsfirmlyattachedtothesubstrate,evenundermechanicalstressorchangesintemperatureandhumidity.

Moreover,thechemicalpropertiesoftheaminosilanegroupsalsoprovideadditionalfunctionalitytothepolymerthinfilm.Forexample,aminosilane-functionalizedpolymercanbeusedinbiosensorstoimprovethesensitivityandselectivityofbiomoleculedetection.Theaminosilanegroupcanfacilitatethecovalentattachmentofbiomoleculesontothepolymerthinfilmsurface,leadingtomorestableandefficientsensingperformance.

Inconclusion,theincorporationofaminosilane-functionalizedpolymerintoepoxyresinhasshowngreatpotentialinenhancingthetribologicalpropertiesofpolymerthinfilmsonSCSsubstrates.Thisapproachcanbefurtherexploredforitsuseinvariousapplications,suchasprotectivecoatingsandmicro/nano-manufacturing.Theresultsofthisstudyprovideimportantinsightsforthedesignanddevelopmentofpolymerthinfilmswithimprovedperformanceandfunctionality.Apartfromtheapplicationsmentionedabove,aminosilane-functionalizedpolymercanalsobeusedasahydrophilicsurfacemodifier.Byintroducinghydrophilicgroupsintothepolymerthinfilm,itcanreducesurfaceenergyandpromotethewettabilityofthesubstratesurface.Thisisparticularlyusefulforsurfacesthatneedtobewettedbyaqueoussolutionsorbiologicalfluids,suchasmicrofluidicdevicesandmedicalimplants.

Moreover,aminosilane-functionalizedpolymercanalsobeusedtocontrolthesurfacemorphologyofthesubstrate.Whenthepolymerthinfilmisself-assembledonthesubstratesurface,theaminosilanegroupscaninteractwiththesubstratesurface,leadingtotheformationofawell-definedsurfacepatternornanostructure.Thiscanbeusefulforapplicationssuchassurface-enhancedRamanscattering(SERS),wherethesurfacemorphologyofthesubstratecangreatlyaffecttheSERSintensity.

Theuseofaminosilane-functionalizedpolymercanalsoimprovethebiocompatibilityofthesubstrate.Theaminosilanegroupcanfacilitatethecovalentattachmentofbioactivemolecules,suchaspeptidesandgrowthfactors,ontothesubstratesurface.Thiscanenhancecelladhesion,proliferation,anddifferentiation,makingitavaluableapproachfortissueengineeringandregenerativemedicine.

Inconclusion,theincorporationofaminosilane-functionalizedpolymerintoepoxyresinoffersaversatileplatformforthedevelopmentofpolymerthinfilmswithtailoredpropertiesandfunctionalities.Thisapproachcanbeappliedtoawiderangeofapplications,includingtribology,surfacemodification,micro/nano-manufacturing,biosensors,SERS,andbiomedicalengineering.Thecombinationofuniquechemicalandphysicalpropertiesofaminosilane-functionalizedpolymerwiththerobustnessandversatilityofepoxyresinprovidesapromisingavenueforthedesignandfabricationofadvancedmaterials.Besides,aminosilane-functionalizedpolymercanalsobeutilizedinthepreparationofantifoulingcoatings.Theamphiphilicnatureandhydrophilicpropertiesofthepolymermakeitaneffectivecandidateforcoatingvarioussubstrates,suchasmembranes,metalsurfaces,andnavalvessels,toresistbiofouling.Aminosilane-functionalizedpolymer-basedcoatingshaveshownimpressiveresultsinminimizingtheaccumulationofmicroorganismsandbacteria,ultimatelyreducingthechancesofbiofoulingandconsequentdeteriorationofthesurface.

Furthermore,theuniquefeaturesofaminosilanesalsomakethemapreferredchoiceforcross-linkingagentsinpolymercomposites.Aminosilanescanreactfirmlywithorganicandinorganicmaterials,whichmakethemsuitableforimprovingth