Investigation of dielectric spectrums, relaxation processes, and intermolecular interactions of primary alcohols, carboxylic acids, and their binary mixtures

An easy-to-integrate and easy-to-calibrate circular-coaxial waveguide junction is proposed for the broadband dielectric characterization of liquid from 100 MHz to18 GHz. The dielectric spectrums of four monohydroxy alcohols (methanol, ethanol, 1-propanol, and 1-butanol), four monocarboxylic acids (formic, acetic, propionic, and oleic acids), and their binary mixtures were measured. Their relaxation parameters were retrieved by the suitable Debye relaxation models to determine excess permittivity, excess Gibbs activation energies, Kirkwood correlation factors, and Bruggeman factors of the four carboxylic acid-ethanol mixtures. These data can be consistently interpreted by different microscopic processes, including the association and dissociation of hydrogen-bound networks under molecular interaction, the parallel or antiparallel orientational rearrangement between heterogeneous dipoles, and the steric hindrance due to the alkyl group. This work not only provides a deeper insight into the fundamental nature of the relaxation processes in polar-polar mixtures but also presents valuable data for esterification process designs in industrial productions.