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Abstract
In our research described here attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was applied to investigate the O–H stretching band for various solutions of the polyethylene glycol 400 (PEG400) in water under the effects of pH and the concentration of propylammonium acetate ionic liquid (IL) volume added to the solution. The Gaussian deconvolution of the O–H stretching band into five sub-bands to describe the frequency components related to each coordination type was carried out. We have shown that the coordination type found depended on the interaction between water molecules and PEG400 chains for the three pHs tested and the IL are the same types as those present in pure bulk water. Therefore, we associated and classified the coordination n types as follows: the tri-coordinated double-donor type (3DD), the 4-coordinated molecules (4), the two coordinated single-donor type (2SD), and the tri-coordinated single-donor type (3SD), from low to high frequencies, respectively. We note that the integrated intensity and the full width at half maximum of individual sub-bands associated with each coordination type depended on the local environment of the hydrogen bonds and thus the physical properties of the mixtures studied.
Acknowledgments
This paper is specially dedicated to the memory of Dr. Naoufel Ghaouar. The authors are much indebted to Prof. A. Abdelghani for his excellent technical assistance. We are also very grateful to Dr. R. Zarrougui, Laboratory of Useful Materials, National Institute for Research and Physico-Chemical Analysis, Technological Pole, Sidi-Thabet Tunis, for his collaboration to get the ionic liquids used in this work. Our work was supported by the Ministry of Superior Education and Scientific Research and Technology of Tunisia.