Test of the Einstein-Debye Relation in Supercooled Dibutylphthalate at Pressures up to 1.4 GPa

Abstract

Broadband dielectric measurements were carried out on di-n-butyl phthalate (DBP) under isothermal conditions at hydrostatic pressures up to 1.6 GPa. A comparison of the dielectric relaxation times with the viscosity revealed that no breakdown of the Einstein-Debye relation is induced by high compression. This absence of any decoupling is attributed to the weak intermolecular cooperativity of DBP and its negligible change with pressure. Because of the latter, the dielectric spectra conform to time-pressure superpositioning.

Classical EHL Versus Quantitative EHL: A Perspective Part II—Super-Arrhenius Piezoviscosity, an Essential Component of Elastohydrodynamic Friction Missing from Classical EHL

“…However, excellent agreement in the derivative analysis has been demonstrated for propylene carbonate [15] for viscosity compared with relaxation time. Viscosity and dielectric relaxation time for dibutyl phthalate can be described by the same super-Arrhenius function for pressure to 1.4 GPa [16]. In fact, the Paluch [17] equation for the pressure-viscosity effect at high pressure, below, is the analog of the Johari and Whaley equation for the pressure dependence of relaxation time.…”

Liquid dynamics in partially crystalline glycerol

“…The main relaxation process, referred to as the α relaxation, is cooperative in nature and can be measured as a response to a wide range of external perturbations, for instance mechanical or electrical 6 . The glass-formers community has widely exploited the imaginary part of the complex dielectric permittivity because of its high sensitivity to external factors such as temperature and pressure, and also to microscopic properties of the substance such as its degree of order, physical interactions with the surroundings, and geometrical confinement among others [7][8][9][10][11][12][13] . Glycerol (propane-1,2,3-triol) is one of the most studied molecular glass-formers, principally for its extremely low tendency to crystallize [14][15][16][17][18][19][20] .…”

On the correlation between fragility and stretching in glass-forming liquids

“…Figure 4 shows the density dependence of the alpha-relaxation time along the four different isotherms, the atmospheric-pressure isobar and the 230 MPa isobar. We have also included the room-temperature dielectric data of Paluch et al [31]. For DBP the viscosity data and the dielectric relaxation time do not decouple under pressure [25], and we have therefore also included the room-temperature viscosity data of Cook et al [31].…”

“…Logarithm of the alpha-relaxation time of DBP versus density (see the text regarding the calculation of density). Included are data from this work along with dielectric data from figure 3 in reference [31], and viscosity data from reference [29]. The viscosity data are shifted arbitrarily on the logarithmic scale in order to make the absolute values correspond to the dielectric data of reference [31], which are taken at the same temperature.…”