FTIR技术在高分子薄膜表征中的应用

UseofFTIRinpolymericthinfilmsFeichenYangFTIR(Fouriertransforminfraredspectroscopy)isatechniquethatusesFouriertransformtoconverttherawdataofinfraredabsorptionortransmissionintoainfraredspectrum.Essentially,itmeasurestheenergiesthatarecorrespondenttothevibrationofatomsinmoleculesormacro-molecules.ThesimplestapplicationofFTIRonpolymersisthatFTIRcanhelptoidentifythefunctionalgroupsinpolymers.Bycomparingthe‘fingerprintregion’ofaobtainedsampletothatofastandardsample,researcherscanalsoidentifyanunknownpolymer.Inthemeantime,researcherscanuseFTIRtomeasuretheconcentrationofacertainfunctionalgroup,todeterminetheextentofreaction.Forexample,HelmutReineckeetal[1]usedtheintegratedIRabsorbancein1450-1580cm-1thatincreaseswiththenumberofreactioncirclestoprovetheincreasingnumberofmonomersinthepolymerthinfilm.Besidesthat,whenit’susedspecificallyonpolymers,FTIRhavesomeuniqueapplications.First,sincethebondbendingandvibratingmotionsofatomsarenotcompletelyirrelevantwithotheratomsnearby,FTIRcanhelpdeterminethetatcticityofpolymers.Forinstance,DalmoMandellietal[2]usedFTIRwithmultivariatecalibrationtodeterminethetacticityofpolypropane.Usingsimilarprinciple,FTIRcanalsohelpdeterminetheconformationofpolymerchainsorthecrystallinityofapolymer.ByusingFTIRspectroscopyandcurve-fittingtechniques,YoshioInoueetal[3]developedaproceduretodeterminethecrystallinityofpoly(ε-Caprolactone).Ifweusepolarizedinfraredlightastheincidentlight,FTIRcandeterminetheorientationofpolymerinthinfilmsorinpolymerbrushes.Sincelightcanonlybeabsorbedwhenthedirectionoflightpolarizationisparalleltothevibrationtransitionmoment,thepolarizedlightcanonlybeabsorbedbyvibrationincertaindirections.BycomparingparallelFTIRspectrumandtheperpendicularFTIRspectrumofapolymerfilmsample,onecandeterminewhetherthepolymersarerandomlydepositedoraligned.Forexample,JohnFRaboltetal[4]usedpolarizedFTIRtodeterminetheorientationsofelectrospunNylon-6nanofibers.Inconclusion,bydeterminethevibrationmodeofatomsinpolymericthinfilms,FTIRcouldbeusedtoidentifypolymer,monitorreaction,determinethetacticityofpolymer,andmeasuretheorientationanditsdistribution.References:[1]Lomadze,N.,Perez,M.,Prucker,O.,Ruhe,J.,&Reinecke,H.(2010).Step-and-RepeatAssemblyofMolecularlyControlledUltrathinPolyaramideLayers.Macromolecules,43(21),9056-9062.[2]Ozzetti,R.A.,DeOliveiraFilho,A.P.,Schuchardt,U.,&Mandelli,D.(2002).DeterminationoftacticityinpolypropylenebyFTIRwithmultivariatecalibration.Journalofappliedpolymerscience,85(4),734-745.[3]He,Y.,&Inoue,Y.(2000).NovelFTIRmethodfordeterminingthecrystallinityofpoly(ε‐caprolactone).Polymerinternational,49(6),623-626.[4]Lee,K.H.,Kim,K.W.,Pesapane,A.,Kim,H.Y.,&Rabolt,J.F.(2008).PolarizedFT-IRstudyofmacroscopicallyorientedelectrospunnylon-6nanofibers.Macromolecules,41(4),1494-1498.