CC BY
3LD-P-3
The 30th International Conference on Advanced Laser Technologies
ALT'23
Raman monitoring of structural evolution of glycols aqueous solutions on various substrates
S.O. Liubimovskii1, V.S. Novikov1, E.A. Sagitova1, V.V. Kuzmin1, P.V. Ivchenko23, G.Yu. Nikolaeva1
1-Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov St. 38, 119991 Moscow, Russia
2- Chemistry Department, M.V. Lomonosov Moscow State University, Leninskie Gory 1(3), 119991 Moscow, Russia 3- A. V. Topchiev Institute of Petrochemical Synthesis of the Russian Academy of Sciences, Leninsky avenue 29, 119991
Moscow, Russia
Aqueous solutions of ethylene glycol (EG, HOCH2CH2OH) and 1,3-propylene glycol (1,3-PG, HOCH2CH2CH2OH) are widely used as cryoprotectants and antifreezes, in particular as deicing fluids for ground deicing of aircrafts. The relative contents of the glycol and water determine the physicochemical properties of the solutions, including the freezing point, thermal conductivity and viscosity. Thus, development of effective methods of glycols aqueous solutions structural characterization is very much in demand for the fundamental researches and numerous applications.
At deposition on substrates, the polar and structurally flexible molecules of glycols can change their conformational states and form ordered structures on a surface. Besides, due to various rates of evaporation of the glycols and water, chemical composition of the solutions on substrates can change significantly with time.
Recently, we developed Raman method for the glycol content evaluation in aqueous solutions, which can be used down to the glycol content of 1 mol.% [1]. In this work wе used this method to study the structural evolution of 1% aqueous solutions of EG and 1,3-PG on various substrates as a function of period of time elapsed from the moment of casting of the solution on a substrate. We revealed that the conformational composition of the glycol molecules in the aqueous solutions on the substrates changes insignificantly compared with that of liquid glycols and glycol aqueous solutions. Analysis of the OH stretching band intensity in the Raman spectra of the solutions on the substrates showed that after application of the solution on the substrates the content of water in the solutions decreases fast. The change in relative contents of glycol and water on substrates depends on the chemical structure of glycol and material of the substrate. In particular, we revealed that the rate of water evaporation is greater on nickel substrate compared to silicon substrate (Fig. 1). We found out that some water remains in the solution on the substrate even an hour after the application of the solution.
1. Liubimovskii S.O., Novikov V.S., Ustynyuk L.Yu., Ivchenko P.V., Prokhorov K.A., Kuzmin V.V., Sagitova E.A., Godyaeva M.M., Gudkov S.V., Darvin M.E., Nikolaeva G.Yu. Raman structural study of ethylene glycol and 1,3-propylene glycol aqueous solutions. // Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 2023. - V. 285. - Art № 121927.
liubimovskii@kapella.gpi.ru
1% EG solution
2600 2800 3000 3200 3400 3600 3800 4000 Wavenumber, cm"1
2600 2800 3000 3200 3400 3600 3800 4000 Wavenumber, cm 1
Fig. 1. Temporal evolution of Raman spectra of 1% EG solution on nickel and silicon substrates.
