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

The complex dielectric spectra for mixtures of unbranched monohydric alcohols with n-alkanes have been measured between 1 MHz and 18 GHz at various mole fractions xCnOH of the alcohols (0.2⩽xCnOH⩽1). Within the frequency range of measurements the spectra exhibit two dispersion/loss regions which can be analytically well represented by a Davidson–Cole-type and a Debye-type relaxation term, respectively. The relaxation parameters are discussed in terms of a wait-and-switch model 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 of the hydrocarbon chains, divide into two groups. Structural features of the alcohol/n-alkane mixtures are proposed to account for the characteristic behavior of both groups of liquids as a function of alcohol content.