Broadband dielectric measurements of primary linear monohydroxy alcohols with microwave microfluidic spectroscopy

Abstract

Dielectric spectroscopy can provide information about the relaxation dynamics and intermolecular interactions in fluids. The past century of research has resulted in many hypotheses about intermolecular interactions in alcohols, including hydrogen bonding dynamics. In spite of extensive efforts to measure the dielectric properties of alcohols, there is a range of specificity of results in the literature. The range of reported values in existing data makes it challenging to validate models of relaxation dynamics and examine trends. Here, we report the dielectric spectra of eight primary linear monohydroxy alcohols, with accompanying uncertainties, measured at 25 °C from 100 MHz to 110 GHz using microwave microfluidic spectroscopy. The spectra of alcohols were fitted with a model containing two relaxations: a dominant Debye relaxation and a higher frequency non-Debye relaxation. We validated our fitting approach by comparing the residuals to the uncertainties. We found that the Debye relaxation changes systematically as a function of the number of carbons in the alkyl chain, decreasing in magnitude and increasing to higher time constants. The non-Debye relaxation also shifts downward in frequency as the chain length increases. Overall, these results are a comprehensive set of broadband dielectric spectra that can be used to test and validate models for intermolecular interactions in alcohols.