Charge Transport and Structural Dynamics in Carboxylic-Acid-Based Deep Eutectic Mixtures

Abstract

Charge transport and structural dynamics in the 1:2 mol ratio mixture of lidocaine and decanoic acid (LID-DA), a model deep eutectic mixture (DEM), have been characterized over a wide temperature range using broad-band dielectric spectroscopy and depolarized dynamic light scattering. Additionally, Fourier transform infrared spectroscopy measurements were performed to assess the degree of proton transfer between the neutral parent molecules. From our detailed analysis of the dielectric spectra, we have determined that this carboxylic-acid-based DEM is approximately 25% ionic at room temperature. Furthermore, we have found that the characteristic diffusion rate of mobile charge carriers is practically identical to the rate of structural relaxation at all measured temperatures, indicating that fast proton transport does not occur in LID-DA. Our results demonstrate that while LID-DA exhibits the thermal characteristics of a DEM, its charge transport properties resemble those of a protic ionic liquid.

Evolution of microscopic heterogeneity and dynamics in choline chloride-based deep eutectic solvents

“…The depression in melting temperature is typically attributed to the complexation of the HBA, specifically the ions in salt-containing DESs, by the HBD through hydrogen bonding 15 , 16 , 19 . Hydrogen bonded networks (HBN) exist in pure HBDs, and these networks are characterized by unique local and supramolecular dynamics 21 – 23 . Moreover, in lithium salt and amide-based DESs, Kaur et al and Subba et al confirmed the existence of spatial and temporal nanoscale heterogeneity, respectively, which likely results from segregated ionic and HBD domains 24 , 25 .…”

Translational and reorientational dynamics in deep eutectic solvents

“…Nevertheless, only a few dielectric investigations of DESs were reported until now. 12,13,[16][17][18][19][20] Interestingly, a recent dielectric study of three DESs, performed by some of the present authors, 13…”

Deep Eutectic Solvents for Pretreatment, Extraction, and Catalysis of Biomass and Food Waste

“…Moreover, for materials of an ionic nature, dielectric spectroscopy is an effective method by which to understand the mechanisms related to charge transport [152]. Despite many studies on ILs, only a few studies on the dielectric properties of DESs have been performed [152,153,154,155,156,157,158,159]. For example, Griffin et al [159] utilized broadband dielectric spectroscopy in combination with depolarized dynamic light scattering to explore the charge transport and structural dynamics of a deep eutectic mixture, {Lidocaine:2Decanoic acid}.…”