Comparative investigations on α relaxation and conductivity of probe ions in a series of small molecular liquids

Abstract

The coupling between translational motion and rotational motion in liquids is one of the long-standing concerns in condensed matter physics. The relaxation times of α relaxation and probe ion conductivities in a series of small molecular liquids, 15 types of single and binary small molecular liquids with different molecular shapes and functional groups when the number of carbon atoms is in a range from 3 to 14, are simultaneously obtained by dielectric spectroscopy method in this work. The results indicate that the coupling between translation and rotation is not directly related to the functional group of liquid molecules, nor very sensitive to the shape nor the size of molecules or ion size. However, the microstructure of liquid is a key factor affecting the coupling between translation and rotation. In other words, when the microstructure of the liquid is unchanged, the dependence of relaxation time on temperature is consistent with the dependence of conductivity reciprocal on temperature, whether in single small molecular liquids or in binary small molecular liquids, which provides a method for measuring relaxation time. The research results also show that the temperature dependence of the conductivity of the impurity ions carried by the liquid itself is consistent with the one of quantitatively doped ions, providing the ideas for investigating the ion conductivity behavior in organic small molecular liquids with low electrolyte solubilities. The experimental results of monohydroxy alcohol are consistent with the viewpoint that α relaxation rather than Debye relaxation corresponds to the system structure relaxation.