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ATR-FTIR spectroscopy and thermogravimetry characterization of water in polyelectrolyte-surfactant hydrogels
- Enev, Vojtěch, Sedláček, Petr, Jarábková, Sabína, Velcer, Tomáš, Pekař, Miloslav
- Colloids and surfaces 2019 v.575 pp. 1-9
- Fourier transform infrared spectroscopy, anionic surfactants, dextran, drying, evaporation, hydrogels, hydrogen, models, thermogravimetry
- Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and thermogravimetric analysis (TGA) were evaluated as useful techniques to study bulk and hydration water in hydrogels. Hydrogels formed by cationized dextran (DEAE-dextran) and anionic surfactants were used as model materials. The IR technique was applied both on fresh samples and on dehydrating samples during the evaporation process. Not only overall IR spectra but especially the deconvoluted OH band was used in the analysis. IR spectroscopy was shown to provide especially structural information which is nicely complemented by the mainly quantitative data provided by TGA. Significant differences between the dehydration processes for the model gels with different surfactants were revealed. The DEAE-dextran-based hydrogels were characterized by a continuous step dehydration with different drying rates in the initial evaporation period. Three different water subpopulations were identified in all model hydrogel samples. Water molecules in these hydrogels containing a higher concentration of surfactants demonstrated a more ordered hydrogen network, which was formed by subpopulations of pentamers, tetramers and/or distorted pentamers.