Glassy dynamics in polyalcohols: intermolecular simplicity vs. intramolecular complexity

Abstract

Using depolarized light scattering, we have recently shown that structural relaxation in a broad range of supercooled liquids follows, to good approximation, a generic line shape with high-frequency power law...

From Single-Particle to Collective Dynamics in Supercooled Liquids

“…While data for only one temperature per material have been analyzed, studies comparing BDS and PCS spectra reveal that the relaxation time ratio τ M /τ s increases with decreasing temperature. For instance, the value of τ M /τ s for propylene glycol increases by 50% when changing temperature from T = 190 to 175 K. 29 This implies larger values for the memory function retardation parameter J K at higher temperatures, consistent with the notion of…”

“…A good performance of this assumption for liquids at normal (opposed to supercooled) conditions 12,[16][17][18][19] supports this view. However, BDS of low-temperature liquids requires stronger retardation than given solely by the Kirkwood factor and adopting J K /κ < 1 is required (Figures 2 and 29 The orange dotted line is a fit to the PCS data, the grey dashed line and red solid line are based on eq 22 with J K /κ = 1.00 and J K /κ = 0.38, respectively, using g K = 4.76 calculated from Wertheim's theory (Table 1).…”

“…Figure2: Experimental results for the dielectric loss spectrum ε ′′ (ω) (BDS, diamonds) and the photon-correlation susceptibility χ ′′ (ω) (PCS, circles) of propylene glycol at T = 190 K, taken from Böhmer et al29 The orange dotted line is a fit to the PCS data, the grey dashed line and red solid line are based on eq 22 with J K /κ = 1.00 and J K /κ = 0.38, respectively, using g K = 4.76 calculated from Wertheim's theory (Table1).…”

From Single-Particle to Collective Dynamics in Supercooled Liquids

“…While data for only one temperature per material have been analyzed, studies comparing BDS and PCS spectra reveal that the relaxation time ratio τ M /τ s increases with a decreasing temperature. For instance, the value of τ M /τ s for propylene glycol increases by 50% when changing the temperature from T = 190 to 175 K. 29 This implies larger values for the memory function dynamic correlation factor J K (eq 16) at higher temperatures, consistent with the notion of J K ≈ 1 in the fluid state.…”

“…Figure 2. Experimental results for the dielectric loss spectrum ε″(ω) (BDS, diamonds) and the photon correlation susceptibility χ″(ω) (PCS, circles) of propylene glycol at T = 190 K, taken from Boḧmer et al29 The orange dotted line is a fit to the PCS data, and the gray dashed line and red solid line are based on eq 22 with J K /κ = 1.00 and J K /κ = 0.38, respectively, using g K = 4.76 calculated from Wertheim's theory (Table1).…”