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Broadband Dielectric Spectroscopic, Calorimetric, and FTIR‐ATR Investigations of D ‐Arabinose Aqueous Solutions
Author(s) -
Singh Lokendra P.,
Cerveny Silvina,
Alegría Angel,
Colmenero Juan
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201100469
Subject(s) - aqueous solution , dielectric , analytical chemistry (journal) , fourier transform infrared spectroscopy , relaxation (psychology) , chemistry , differential scanning calorimetry , attenuated total reflection , atmospheric temperature range , spectroscopy , infrared spectroscopy , materials science , chromatography , optics , thermodynamics , organic chemistry , psychology , social psychology , physics , optoelectronics , quantum mechanics
The dielectric relaxation behavior of D ‐arabinose aqueous solutions at different water concentrations is examined by broadband dielectric spectroscopy in the frequency range of 10 −2 –10 7 Hz and in the temperature range of 120–300 K. Differential scanning calorimetry is also performed to find the glass transition temperatures ( T g ). In addition, the same solutions are analyzed by Fourier transform infrared (FTIR) spectroscopy using the attenuated total reflectance (ATR) method at the same temperature interval and in the frequency range of 3800–2800 cm −1 . The temperature dependence of the relaxation times is examined for the different weight fractions ( x w ) of water along with the temperature dependence of dielectric strength. Two relaxation processes are observed in the aqueous solutions for all concentrations of water. The slower process, the so‐called primary relaxation process (process‐I), is responsible for the T g whereas the faster one (designated as process‐II) is due to the reorientational motion of the water molecules. As for other hydrophilic water solutions, dielectric data for process‐II indicate the existence of a critical water concentration above which water mobility is less restricted. Accordingly, FTIR‐ATR measurements on aqueous solutions show an increment in the intensity (area) of the OH stretching sub‐band close to 3200 cm −1 as the water concentration increases.