Calculation of dielectric spectra of a glucose-based deep eutectic solvent: Insights from classical molecular dynamics simulation

Abstract

An atomistically detailed force field is employed to investigate the origin of the dielectric spectra of a naturally abundant deep eutectic solvent (NADES) composed of glucose, urea, and water in a 6:4:1 mass ratio at 343 K. The estimated dielectric constant indicates that urea-urea and glucose-glucose self-interactions are the dominant contributors to the total dielectric constant of the system. Tri-exponential fitting of the system’s dipole relaxation dynamics reveals three dielectric loss peaks corresponding to sub-10 picosecond, sub-100 picosecond, and sub-nanosecond relaxation processes. Spectral decomposition into self- and cross-interaction components shows that ultrafast sub-10 picosecond dynamics are absent in the cross-interactions. Molecular reorientations and hydrogen-bond relaxations are examined as potential mechanisms underlying the observed macroscopic dielectric behaviour. The analysis indicates that sub-nanosecond dynamics primarily arise from large-scale hydrogen-bond network reorganizations, whereas the intermediate and faster relaxation modes are associated with partial hydrogen-bond breaking and rapid rupture-reformation events occurring on sub-picosecond to picosecond timescales.