A dielectric spectroscopy study of deep eutectic mixtures of glycerol and hydroxyl ammonium chloride in liquid and glassy states

Abstract

This paper reports the molecular dynamic study of ionic deep eutectic (DE) mixtures prepared by mixing glycerol (Gly) with hydroxyl ammonium chloride (HACL). Here, the dielectric relaxation spectroscopy over wide ranges of frequency (10−1-107 Hz) and temperature (193–323 K), was employed to access the dynamic observables in liquid and glassy states. Fourier-transform infrared spectroscopy (FTIR) revealed that HACL and Gly are associated via the formation of hydrogen bonds between their functional groups. Differential scanning calorimetry (DSC) results indicated that a glass transition temperature slightly changes compared to that of pure Gly. It is worth mentioning that, at low frequencies, where α-relaxation process occurs, electrode polarization and dc conductivity affect the dielectric spectra of both neat and binary DE mixtures. The shape and intensity of the α-process are highly affected, while it is completely masked at higher concentrations due to the predominance of dc conductivity. Further, the dc conductivity of Gly abruptly increased by about 3 orders of magnitude upon adding only 1.5 wt.% HACL due to an increase in both mobility and concentrations of the introduced free ions. With further increase of HACL, it increases at a relatively low rate. Interestingly, the excellent electrical properties of the binary mixture of 1.5 wt.% HACL make it promising candidate in potential applications in the renewable energy field and energy storage devices.