Dielectric Relaxation in Associated Liquids

Abstract

The dielectric properties of the associated liquids butanediol 1,3, 2-methyl pentanediol 2,4, glycerol, and hexanetriol 1,2,6 have been measured over the temperature range —20° to +10°C, and over a frequency range of 0.01 to 1200 Mc/sec. Dielectric relaxation times and their distributions have been determined and indicate the following: (a) All four liquids exhibit an asymmetric distribution of relaxation times of the Davidson—Cole form. (b) With the exception of hexanetriol 1,2,6, the distribution of relaxation times becomes narrower with increasing temperature. It is proposed that groups (regions of appreciable order) exist in these liquids, and that dielectric orientation is closely related to the structural breakup of these groups, this breakup being a necessary condition for dipole reorientation. It is further proposed that the structural breakup is a cooperative process which does not proceed exponentially, therefore giving rise to a nonexponential decay of dielectric polarization. This concept offers an explanation for the observed distribution of relaxation times. The temperature dependence of the width of the distribution is explained by assuming that the group-size decreases with increasing temperature, and that as the groups become smaller, the structural-decay process becomes more exponential.

The defect diffusion model and the properties of glasses and liquids

“…The average value of each of the bestfit parameters from Ref. [6] for five sources of data for both glycerol [6,[14][15][16][17] and PPG 4000 [18][19][20][21][22][23] are listed in Table 1 for the standard Vogel temperature equation (g = 2). The average values for the 3/2 power law (g = 3) are listed in Table 2.…”

Liquid properties of oligomers. Comparison of relaxational properties of propylene glycol oligomers with those of ethylene glycol oligomers

“…The dielectric properties of the vinylacetate oligomers and the related acetate molecules were investigated in detail to clarify the chain length dependences of the relaxational behaviors of vinylacetate molecules [3,4,5,6]. The liquid and the supercooled polyhydroxy compounds show the asymmetric Davidson-Cole-type relaxation [7,8,9]. It is mathematically proved that the asymmetric distribution of relaxation times is associated with the cooperative mechanism of dielectric relaxation [10].…”

Chain Dynamics of Polystyrene in High Viscosity Solvents Studied by the Fluorescence Depolarization Method

“…For example, Khudayarov et al 28 reported that the distribution of relaxation times in glycerides results from the orderliness of liquids by inter-204 molecular interaction. Moreover, McDuffie and Litovitz 29 reported that in associated solutions there is a significant difference between the temperature dependence of the viscosity and that of relaxation time measured by dielectric relaxation, but at lower temperatures the temperature dependence was the same. Furthermore, they reported that a structural group or a cluster exists in the liquid state, and that the group size decreases with increasing temperature with only a small group of molecules remaining at high temperatures.…”