FTIR−ATR Studies of the Structure and Dynamics of Water Molecules in Polymeric Matrixes. A Comparison of PET and PVC

Abstract

We report a systematic FTIR study of the perturbation of water “sorbed” into the polymers PET and PVC as a function of crystallinity (PET) or plasticizer content (PVC). Band shapes of the composite ν(OH) band of H2O obtained by the ATR technique have been fitted to individual components,corresponding to those recently found for pure water itself. A detailed quantitative analysis of the frequency shifts and relative intensties has led to conclusion that these component bands show direct evidence for the breaking of the water network in the polymer matrix and that this process depends on the polymer chemical and/or physical properties. Evidence is also found for interactions of water with the polymer at the lower end of the hydrogen bond interaction scale. The component band relative intensities (compared with those of pure water) have been used to compute an intensity enhancement parameter, P, which is a measure of the perturbation of a particular water distribution due to dissolution in the polymer matrix. For PET, P varies systematically with density, reflecting the ability of water to penetrate the polymer microstructure. For PVC the plasticizer content (and hence T g) has a considerable influence on the sorption (and swelling) process and on the equilibrium content and state of water. Thus, ATR-FTIR has been used for the first time to demonstrate,via intensity enhancement, the extent of electronic perturbation at a polymer/water interface.

Hydration of polysaccharide hyaluronan observed by IR spectrometry. I. Preliminary experiments and band assignments

“…Once this difficulty has been recognized, it can be avoided [1][2][3] and IR spectroscopy can be a powerful tool to obtain structural information on the behavior of H 2 O molecules embedded in macromolecules. Using thin films we have thus been able to follow the hydration process of a protein, bovine serum albumin (BSA), and to determine the hydrogen bond configurations or interaction configurations that H 2 O molecules adopt when entering this protein 4,5 during hydration.…”

Evidence of the existence of the low-density liquid phase in supercooled, confined water

“…However, the measured peak positions are the same, within the experimental error, whereas differences may be observed in the corresponding intensities and linewidths. However, a careful comparison between Raman and FTIRattenuated total reflection (ATR) measurements in water shows that experimental full widths at half maximum (FWHM) coincide within a 15% (or less) error window (34). This result means that results of the two techniques can be used complementarily to explore the water vibrational dynamics.…”

ATR-FTIR spectroscopic analysis of sorption of aqueous analytes into polymer coatings used with guided SH-SAW sensors

“…Attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR) has been shown to be a useful technique for analysis of aqueous solutions where the strong infrared absorbance of water precludes transmittance measurements [10] and has been utilized to analyze polymer films [11], water diffusion into polymer films [12], and analyte sorption into polymers [13][14][15]. A number of chemical sensors have been implemented for direct detection of analytes in both air and water based on ATR-FTIR strategies [16][17][18].…”

“…An absorption spectrum can be obtained by monitoring the intensity of reflected IR radiation and using a Beer-Lambert law expression similar to equation (4) where the path length l is replaced by an effective thickness, de, which is determined from the number of reflections and the wavelength-dependent dp [11,15]. The depth of penetration of the evanescent field is ~ 1-2 m from the surface of the prism for the wavelength range of interest in this study.…”