Dielectric properties of water in Triton X-100 (nonionic detergent)–water mixtures

Abstract

Dielectric measurements were carried out for mixtures of Triton X-100 (TX, anonionic detergent with a poly(ethylene oxide) chain) and water with or withoutelectrolytes over a frequency range of 1 MHz to 10 GHz to study the structureand dynamics of water molecules in the mixtures. Dielectric relaxation wasfound above 100 MHz, being assigned to the dielectric relaxation of water. Theintensity of the dielectric relaxation was proportional to the water content above0 °C.Below the freezing temperature of bulk water, the relaxation intensity decreased at TX concentrations(CTX) below 50 wt%at −10 °C and below60 wt% at −20 °C because frozen water shifts the dielectric relaxation to a frequencyregion far below 1 MHz. This indicated that there is no bulk water atCTX above 50 wt% and that at least two water molecules per ethylene oxide (EO) unit are tightlyassociated with the ethylene oxide chain. The low-frequency conductivity of the mixtures ofTX and electrolyte solutions was well represented by Bruggeman’s mixture equation atCTX below 40 wt%, if two water molecules per EO unit form an insulating shell surrounding TXmicelles.