Comparison of Dielectric and Mechanical Relaxation in Associated Liquids

Abstract

A comparison is made of existing dielectric and ultrasonic shear and compressional relaxation data in several associated liquids including glycerol, hexanetriol 1,2,6, butanediol 1,3, 2‐methyl pentanediol 2,4, and n‐propyl alcohol. The data show that the pressure and temperature dependences of the dielectric time τ_D and the volume relaxation times τ_v are very similar indicating a close connection between the two processes. It is proposed here that cooperative effects cause the distribution of mechanical relaxation times in these liquids as well as the non‐Arrhenius behavior of the temperature dependence of the shear and volume viscosities. It is further suggested that structural relaxation is a rate‐determining step in the dielectric relaxation process and that the origin of the distribution of dielectric times is the distribution of structural relaxation times.