Etalon features in infrared spectra of stratified samples, their influence on the interpretation, and methods to circumvent their presence in infrared spectra have been in discussion for decades. This paper focuses on the application of a method originally developed to remove interference fringes in the mid-infrared spectra for far-infrared Fourier transform spectroscopy on thin polymer films. We show that the total transmittance reflectance technique, commonly used for mid-infrared, also works successfully in the far-infrared spectral range where other approaches fail. Experimental spectra obtained by such technique are supported by model calculations and reveal the possibility and limits to obtain almost undisturbed far-infrared spectra which are suitable to determine low-energy vibrations of ionomer salts under certain sample conditions.
SahuA.K.PitchumaniS.SridharP., et al.“Nafion and Modified-Nafion Membranes for Polymer Electrolyte Fuel Cells: An Overview”. Bull. Mater. Sci. 2009. 32(3): 285–294.
2.
SchabergM.AbuluJ.HaugenG., et al.“New Multi Acid Side-Chain Ionomers for Proton Exchange Membrane Fuel Cells”. ECS Trans. 2010. 33(1): 627–633.
3.
DanilczukM.LancuckiL.SchlickS., et al.“In-Depth Profiling of Degradation Processes in a Fuel Cell: 2D Spectral-Spatial FTIR Spectra of Nafion Membranes”. ACS Macro Lett. 2012. 1(2): 280–285.
4.
MarcottC.AwataniT.YeJ., et al.“Review of Nanoscale Infrared Spectroscopy Applications to Energy Related Materials”. Spectrosc. Eur. 2014. 26(1): 18–22.
5.
PuskarL.RitterE.SchadeU., et al.“Infrared Dynamics Study of Thermally Treated Perfluoroimide Acid Proton Exchange Membranes”. Phys. Chem. Chem. Phys. 2017. 19(1): 626–635.
6.
MatteraV.D.PelusoS.L.TsatsasA.T., et al.“Spectroscopic and Thermal Studies of Ionic Interactions in Ionomers”. ACS Symp. Ser. 1986. 320: 54–65.
7.
MatteraV.D.RisenW.M.“A Far-Infrared Study of Ionic Interactions in Poly(styrene Sulfonic Acid) Ionomers”. J. Polym. Sci. Polym. Phys. Ed. 1984. 22(1): 67–77.
8.
BawaganA.D.O.HamrockS.J.SchabergM., et al.“Far-Infrared Studies on Nafion and Perfluoroimide Acid (PFIA) and their Alkali Salts”. Vib. Spectrosc. 2014, pp. 1–5.
9.
PhonyiemM.ChaiwongwattanaS.Lao-NgamC., et al.“Proton Transfer Reactions and Dynamics of Sulfonic Acid Group in Nafion”. Phys. Chem. Chem. Phys. 2011. 13(23): 10923–10939.
10.
HorinekD.MamatkulovS.I.NetzR.R.“Rational Design of Ion Force Fields Based on Thermodynamic Solvation Properties”. J. Chem. Phys. 2009. 130(12): 124507-1–124507-21.
11.
ElliottJ.A.PaddisonS.J.“Modelling of Morphology and Proton Transport in PFSA Membranes”. Phys. Chem. Chem. Phys. 2007. 9(21): 2602–2618.
12.
YuT.H.ShaY.LiuW.-G., et al.“Mechanism for Degradation of Nafion in PEM Fuel Cells from Quantum Mechanics Calculations”. J. Am. Chem. Soc. 2011. 133(49): 19857–19863.
13.
GundeM.K.“Optical Effects in IR Spectroscopy: Thickness-Dependent Positions of Absorbance Lines in Spectra of Thin Films”. Appl. Spectrosc. 1992. 46(2): 365–372.
14.
MayerhöferT.G.MutschkeH.PoppJ.“The Electric Field Standing Wave Effect in Infrared Transmission Spectroscopy”. Chem. Phys. Chem. 2017. 18(20): 2916–2923.
15.
KučírkováA.NavrátilK.“Undesirable Occurrence of the Interference Fringes in IR Transmittance Spectra”. Scr. Fac. Sci. Nat. Univ. Masaryk. Brun. 1993. 23: 5–27.
16.
TeolisB.D.LoefflerM.J.RautU., et al.“Infrared Reflectance Spectroscopy on Thin Films: Interference Effects”. Icarus. 2007. 190(1): 274–279.
17.
NeriF.SaittaG.ChiofaloS.“A Simple Procedure to Remove the Interference Fringes from Optical Spectra”. J. Phys. E. 1987. 20(7): 894–896.
18.
FarringtonP.J.HillD.J.T.O’DonnellJ.H., et al.“Suppression of Interference Fringes in the Infrared Spectra of Thin Polymer Films”. Appl. Spectrosc. 1990. 44(5): 901–903.
19.
GamskyC.J.HowesG.R.TaylorJ.W.“Infrared Reflection Absorption Spectroscopy of Photoresist Films on Silicon Wafers: Measuring Film Thickness and Removing Interference Fringes”. Anal. Chem. 1994. 66(7): 1015–1020.
20.
BrendelR.“The Concept of Effective Film Thickness for the Determination of Bond Concentrations from IR Spectra of Weakly Absorbing Thin Films on Silicon”. J. Appl. Phys. 1991. 69(11): 7395–7399.
21.
MansfieldC.D.RuttH.N.“Evaluation of Multiple Beam Interference Effects in Infrared Gas Spectroscopy”. Meas. Sci. Technol. 1999. 10(3): 206–210.
R.F. Edgar, B.J. Stay. “Techniques for Suppressing Optical Interference Errors in Infrared Film Thickness Gauging”. Presented at: 1985 International Technical Symposium/Europe. Cannes, France; Nov 25–27, 1985. In Proceedings of the SPIE 0590, Infrared Technology and Applications. 1986. Pp. 316–321. 10.1117/12.952000.
24.
TengV.T.ShumakerW.H.“A Technique for Eliminating Interference Fringes from Infrared Spectra of Thin Polymer Films”. Appl. Spectrosc. 1986. 40(3): 421–422.
25.
LutinskiC.“Method for Elimination of Interference Fringes in Spectra of Thin Films”. Anal. Chem. 1958. 30(12): 2071–2072.
26.
DoreP.NucaraA.CannavòD., et al.“Infrared Properties of Chemical-Vapor Deposition Polycrystalline Diamond Windows”. Appl. Opt. 1998. 37(24): 5731.
27.
HarrickN.J.“Transmission Spectra Without Interference Fringes”. Appl. Spectrosc. 1977. 31(6): 548–549.
28.
BassanP.LeeJ.SachdevaA., et al.“The Inherent Problem of Transflection-Mode Infrared Spectroscopic Microscopy and the Ramifications for Biomedical Single Point and Imaging Applications”. Analyst. 2013. 138(1): 144–157.
29.
ZawodzinskiT.A.NeemanM.SillerudL.O., et al.“Determination of Water Diffusion Coefficients in Perfluorosulfonate Ionomeric Membranes”. J. Phys. Chem. 1991. 95(15): 6040–6044.
30.
Abo-BakrM.FeikesJ.HolldackK., et al.“Brilliant, Coherent Far-Infrared (THz) Synchrotron Radiation”. Phys. Rev. Lett. 2003. 90(9): 094801–1–094801-4.
31.
SchusterK.“Anwendung der Vierpoltheorie auf die Probleme der optischen Reflexionsminderung, Reflexionsverstärkung und der Interferenzfilter”. Ann. Phys. 1949. 439(6): 352–356.
32.
AbelèsF.“Recherches sur la propagation des ondes électromagnétiques sinusoïdales dans les milieux stratifiés”. Ann. Phys. (Paris). 1950. 12(5): 596–640.
33.
H. Wolter. “Optik dünner Schichten”. In: S. Flügge, editor. Grundlagen der Optik. Berlin: Springer-Verlag, (1956). Pp. 461–554.
34.
MayerhöferT.G.MutschkeH.PoppJ.“Employing Theories Far Beyond Their Limits – The Case of the (Boguer-) Beer–Lambert Law”. Chem. Phys. Chem. 2016. 17(13): 1948–1955.
35.
BirchJ.R.“The Far-Infrared Optical Constants of Polypropylene, PTFE and Polystyrene”. Infrared Phys. 1992. 33(1): 33–38.
36.
JohnsonK.W.RaboltJ.F.“Far Infrared Measurements on the 19℃ Phase Transition in Polytetrafluoroethylene”. J. Chem. Phys. 1973. 58(10): 4536–4538.
37.
LiangC.Y.KrimmS.“Infrared Spectra of High Polymers. III. Polytetrafluoroethylene and Polychlorotrifluoroethylene”. J. Chem. Phys. 1956. 25(3): 563.
38.
RaboltJ.FanconiB.“Raman Scattering from Finite Polytetrafluoroethylene Chains and a Highly Oriented TFE-HFP Copolymer Monofilament”. Macromolecules. 1978. 11(4): 740–745.
39.
A. Röseler. Infrared Spectroscopic Ellipsometry. Berlin: Akademie-Verlag Berlin, (1990). P. 15.
40.
OrdalM.A.LongL.L.BellR.J., et al.“Optical Properties of the Metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the Infrared and Far Infrared”. Appl. Opt. 1983. 22(7): 1099–1120.
41.
CunninghamP.D.ValdesN.N.VallejoF.A., et al.“Broadband Terahertz Characterization of the Refractive Index and Absorption of Some Important Polymeric and Organic Electro-Optic Materials”. J. Appl. Phys. 2011. 109(4): 1–5.
42.
I.S. Gradstein, I.M. Ryshik. Tablizy Integralow, Summ, Rjadow i Proiswedenij (Tables of Integrals, Sums, Series and Products). Moskwa: Gos. Isdat. Fyz.-Mat. Lit., (1963). P. 54.
