Characterization of solvent effect on low-frequency dielectric dispersion and relaxation behaviour of ethylene glycol oligomers

Abstract

The complex relative dielectric function ɛ⁎( ω) = ɛ′ − jɛ″, electric modulus M⁎( ω) = M′ + jM″, alternating current electrical conductivity, and loss tangent tan δ = ɛ″ / ɛ′ spectra of binary mixture of ethylene glycol oligomers (EGOs) namely, ethylene glycol (EG), diethylene glycol (DEG) and poly(ethylene glycol)s (PEGs) of average molecular weight 200, 300, 400 and 600 g mol − 1 with water (W), ethyl alcohol (EA) and 1,4-dioxane (Dx) in the frequency range 20 Hz to 1 MHz were investigated at 298 K. In the lower-frequency range, the EGOs + W, EGOs + EA and EGOs + Dx mixtures show the direct current conductivity behaviour, and their values can be monitored by concentration variation of the mixture constituents, specially in case of EGOs + W and EGOs + Dx mixtures. The frequency value corresponding to tan δ peak, separates the contribution of the bulk and the electrode polarization phenomena, which is used to evaluate the electrode polarization relaxation time. The M″( f) peak frequency value is considered to evaluate the ionic conduction relaxation time. In these binary mixtures, as compared to rigid chain EG and DEG molecules, the flexible chain EGOs of higher molecular weight have significantly different dielectric response.