Dielectric relaxation of hydrogen bonded liquids: Mixtures of monohydric alcohols with n-alkanes

The complex dielectric spectra for mixtures of unbranched monohydric alcoho ls with n-alkanes have been measured between 1 MHz and 18 GHz at various mo le fractions x(CnOH) of the alcohols (0.2 less than or equal to x(CnOH) les s than or equal to1). Within the frequency range of measurements the spectr a exhibit two dispersion/loss regions which can be analytically well repres ented by a Davidson-Cole-type and a Debye-type relaxation term, respectivel y. The relaxation parameters are discussed in terms of a wait-and-switch mo del of relaxation. considering also the effect of the nonpolar hydrocarbon groups in the enthalpy of activation of the dielectric relaxation process. This model allows for a consistent description of the dielectric properties of the alcohol/n-alkane mixtures which, depending on the relative length o f the hydrocarbon chains, divide into two groups. Structural features of th e alcohol/n-alkane mixtures are proposed to account for the characteristic behavior of both groups of liquids as a function of alcohol content. (C) 20 01 American Institute of Physics.