Fig. 4: Dynamics measured from BDS, DMS, and fs-TA spectroscopy.

a Top: The derivative representation of the dielectric loss, \({\varepsilon }_{der}^{{\prime\prime} }[=-\pi /2\,\partial \varepsilon ^{\prime} /\partial ln(\omega )]\), for glycerol at selected temperatures plotted as a function of radial frequency. Bottom: \({\varepsilon }_{der}^{{\prime\prime} }\) of 5 mol% ChCl in glycerol plotted versus radial frequency at the same temperatures shown for glycerol. The solid black lines denote fits that account for the cumulative contributions observed in the mixtures. For glycerol, the fit comprises of a single empirical Havriliak–Negami function, while the fit for 5 mol% ChCl (and all high ChCl concentrations measured) is the linear addition of a Debye function (shaded region), Havriliak–Negami (dotted line) and Random-Barrier Model (dash-dot line). Fits are described in the SI. b The real and imaginary parts of viscosity, \(\eta ^{\prime}\) and η″, for 0, 5, 10, 20, and 33 mol% ChCl in glycerol obtained from a time–temperature superposition as described in the Section “DMS methods”, normalized by the corresponding zero-shear viscosity plotted versus angular frequency normalized by the mechanical structural relaxation rate at each concentration. The dotted line represents the probe wavelength at 590 nm. c Top panel: Steady-state UV–visible absorption of betaine-30, bottom panel: femtosecond transient absorption spectra at indicated delay times. d fs-TA kinetics of betaine-30 in 33 mol% Glyceline at a probe wavelength of 590 nm. The solid line at 0.0 represents the baseline.