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Determination of exact absorption behaviour in the mid‐infrared spectral range of poly(methylmethacrylate) by Fourier transform infrared reflection spectroscopy
Author(s) -
Brogly Maurice,
Bistac Sophie,
Schultz Jacques
Publication year - 1997
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/(sici)1097-0126(199709)44:1<11::aid-pi814>3.0.co;2-4
Subject(s) - specular reflection , materials science , absorption (acoustics) , infrared , infrared spectroscopy , transmittance , refractive index , spectral line , attenuated total reflection , optics , reflection (computer programming) , absorption spectroscopy , diffuse reflection , spectroscopy , diffuse reflectance infrared fourier transform , molecular physics , analytical chemistry (journal) , fourier transform infrared spectroscopy , chemistry , physics , optoelectronics , biochemistry , organic chemistry , chromatography , quantum mechanics , astronomy , photocatalysis , computer science , programming language , catalysis
In the present work we demonstrate that infrared absorption fre‐quencies and band shapes of poly(methylmethacrylate) (PMMA) homopolymers vary strongly with the type of spectra recorded. The reason is that, in general, any measured optical quantity, such as absorption, transmittance or reflectance, is a complicated function of the refractive index, n (ν), and the absorption index, k (ν), of the material. Kramers–Kronig analysis is applied to external reflection spectra from a single polymer surface measured near the normal incidence angle. Absorption spectra, k (ν), are then deduced and used to calculate grazing angle specular reflectance, attenuated total reflectance, diffuse reflectance and transmission spectra. Then, it is shown that the calculated spectrum for each experiment accurately predicts the experimental one, proving that differences are optical artifacts and not true sample differences. Exact peak absorption for PMMA is 1730cm ‐1 and should be taken as a reference value for the calculation of frequency shifts for further physico‐chemical interpretation such as specific interactions or molecular orientation. ©1997 SCI