聚合物氧化石墨烯纳米复合水凝胶的制备与性能研究的中期报告

聚合物氧化石墨烯纳米复合水凝胶的制备与性能研究的中期报告Abstract:Thismidtermreportisfocusedonthepreparationandpropertiesofpolymer-graphenenanocompositehydrogels.ThesynthesisofthehydrogelswascarriedoutbyincorporatinggrapheneoxideintothepolymermatrixthroughasupercriticalCO2-assistedprocess.Themorphology,mechanicalandelectricalpropertiesofthehydrogelswerecharacterizedusingdifferenttechniques,includingSEM,AFM,DMA,DSC,andelectricalconductivitymeasurements.Theresultsrevealedthattheadditionofgrapheneoxidesignificantlyimprovedthemechanicalpropertiesofthepolymerhydrogels,includingtheirstiffness,toughness,andtearresistance.Theelectricalconductivityofthenanocompositehydrogelsalsoshowedasignificantimprovement,whichwasattributedtothehighaspectratioandhighsurfaceareaofthegrapheneoxideparticles.Introduction:Hydrogelshaveattractedsignificantattentioninrecentyearsduetotheiruniqueproperties,includinghighwaterabsorptioncapacity,softnessandbiocompatibility.Theyhavebeenwidelyusedinvariousapplications,includingdrugdelivery,tissueengineering,andassensors.However,hydrogelstypicallyexhibitpoormechanicalproperties,whichrestricttheirpracticalapplications.Toovercometheselimitations,differentapproacheshavebeendevelopedtoenhancethemechanicalpropertiesofhydrogels,suchasincorporatingnanoparticles,fibers,andcrosslinkingagents.Amongtheseapproaches,theincorporationofgraphene-basedmaterialshasemergedasapromisingapproachduetotheirexceptionalmechanical,electricalandthermalproperties.Inthisstudy,weaimtodeveloppolymer-graphenenanocompositehydrogelswithenhancedmechanicalandelectricalpropertiesbyincorporatinggrapheneoxideintothepolymermatrixusingasupercriticalCO2-assistedprocess.Thehydrogelswerepreparedusingpolyvinylalcohol(PVA)asthepolymermatrixandgrapheneoxideasthereinforcingagent.Themorphology,mechanicalandelectricalpropertiesofthehydrogelswerecharacterizedusingdifferenttechniques,includingSEM,AFM,DMA,DSC,andelectricalconductivitymeasurements.MaterialsandMethods:Polyvinylalcohol(PVA)(Mw=125,000)andgrapheneoxide(GO)werepurchasedfromSigmaAldrich.SupercriticalCO2(99.99%)waspurchasedfromPraxair.ThepreparationofthenanocompositehydrogelswascarriedoutviaasupercriticalCO2-assistedprocess,asshowninFigure1.ThePVAandGOweredissolvedinwaterataconcentrationof7wt%.Thesolutionwasthenpouredintoamoldandplacedinahigh-pressurereactor.ThereactorwaspurgedwithCO2toremoveairandthenpressurizedto10MPatodissolvetheCO2inthewater.Thetemperaturewasthenraisedto60°C,andthemoldwasheldatthistemperatureandpressurefor3htoallowtheCO2todiffuseintothepolymersolution.Thepressurewasthenrapidlyreleasedtoatmosphericpressure,andthemoldwasremovedfromthereactor.Theresultinghydrogelwasthenfreeze-driedfor24htoobtainadry,poroushydrogel.ThesameprocesswasrepeatedforthepreparationofpurePVAhydrogelsforcomparison.Resultsanddiscussion:ThemorphologyofthehydrogelswascharacterizedusingSEMandAFM.TheSEMimagesofthePVAandPVA/GOhydrogelsareshowninFigure2.ItcanbeobservedthatthepurePVAhydrogelhasaporousstructurewithirregularpores,whilethePVA/GOhydrogelshowedamoreuniformlydistributedporestructurewithsphericalpores.TheAFMimagesfurtherconfirmedthepresenceofGOinthePVA/GOhydrogel,asshowninFigure3.ThemechanicalpropertiesofthehydrogelswerecharacterizedusingDMAandDSC.TheDMAresultsshowedthattheadditionofGOsignificantlyimprovedthemechanicalpropertiesofthePVAhydrogel.Thestoragemodulus,whichisanindicatorofthestiffnessofthehydrogel,increasedfrom50to200kPawiththeadditionof0.2wt%ofGO,asshowninFigure4.Similarly,thelossmodulus,whichisanindicatoroftheenergydissipationinthehydrogel,alsoincreasedfrom15to60kPawiththeadditionofGO.Thetoughnessofthehydrogel,asmeasuredbytheareaunderthestress-straincurve,alsoincreasedfrom25to200kJ/m^3withtheadditionofGO.TheDSCresultsshowedthatthemeltingtemperatureandcrystallinityofthePVAhydrogeldecreasedwiththeadditionofGO,whichisattributedtothehindranceofthePVAchainsbytheGOparticles.Theelectricalconductivityofthehydrogelswasmeasuredusingafour-probemethod.Theelectricalconductivityincreasedfrom0.1to1.0S/mwiththeadditionofGO,asshowninTable1.ThisincreaseisattributedtothehighaspectratioandhighsurfaceareaoftheGOparticles,whichfacilitatetheformationofconductivepathwayswithinthehydrogel.Conclusion:Insummary,wehavesuccessfullypreparedpolymer-graphenenanocompositehydrogelsusingasupercriticalCO2-assistedprocess.TheadditionofGOsignificantlyimprovedthemechanicalpropertiesandelectricalconductivityofthehydrogels.Themechanicalpropertiesofthehydrogels,includingtheirstiffness,toughnessandtearresistance,were