The characterization of aprotic polar liquids and percolation phenomena in DMSO/water mixtures

Abstract

In the previous papers of our research group it was shown, that the Clausius-Mossotti-Debye equation for the quasi-static dielectric constant ( ε r) can be extended to liquids if the parameter E i / E is introduced. Thus, it is possible to characterize polar liquids with the easily accessible parameter E i / E. This property is also reflected by the fact that the parameter E i / E can be directly related to the empirical E T(30) and the normalized E T N parameter to describe the polarity of liquids proposed by Reichardt (Chem. Rev. 94, 2319-2358) E i corresponds to the local mean field due to close molecule-molecule interactions after the application of an external electric field E. In a recent work of our research group it was also demonstrated that the modified Clausius-Mossotti-Debye equation and the study of the relaxation time can be related to percolation phenomena in binary solvent mixtures leading to a valuable insight of the structure of polar liquids and to a better understanding of binary systems. In the present paper it is demonstrated that percolation phenomena for binary DMSO/water mixtures, become visible due to changes of parameters describing the dielectric spectrums. The interpretation of the percolation effects leads to the following conclusion: DMSO/water mixtures seem to have in the whole range of miscibility the same microscopic structure like water with a coordination number z≈ between 4 and 6 which could be the reason for the high permeability of DMSO through biological membranes. (1) E T N = E T ( solvent ) − E T ( TMS ) E T ( water ) − E T ( TMS ) = E T ( solvent ) − 30.7 32.4