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 x(CnOH) of the alcohols (0.2 less than or equal to x(CnOH) less than or equal to1). 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. (C) 2001 American Institute of Physics.