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Surfactant-Switched Positive/Negative Electrorheological Effect in Tungsten Oxide Suspensions

1
Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Ivanovo 153045, Russia
2
Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Moscow 119991, Russia
*
Author to whom correspondence should be addressed.
Molecules 2019, 24(18), 3348; https://doi.org/10.3390/molecules24183348
Received: 21 August 2019 / Revised: 6 September 2019 / Accepted: 12 September 2019 / Published: 14 September 2019
(This article belongs to the Section Nanochemistry)
The electrorheological (ER) effect was experimentally observed in dielectric suspensions containing tungsten oxide (WO3) modified with surfactant molecules (sodium dodecyl sulfate (SDS) and dodecylamine (DDA)) in electric fields up to several kilovolts per millimeter. The dielectric properties of WO3 suspensions in silicone oil were analyzed, depending on the frequency of the electric field, in the range from 25 to 106 Hz. Unmodified WO3 suspensions, as well as suspensions modified with sodium dodecyl sulfate, were shown to exhibit a positive electrorheological effect, whereas suspensions modified with dodecylamine demonstrated a negative electrorheological effect. The quantitative characteristics of the negative electrorheological effect in the strain–compression and shear regimes were obtained for the first time. Visualization experiments were performed to see the chain structures formed by WO3 particles modified with sodium dodecyl sulfate, as well as for dynamic electroconvection in electrorheological fluids containing WO3 modified with dodecylamine. The negative electrorheological effect was shown to be associated with the processes of phase separation in the electric field, which led to a multiplicative effect and a strong electroconvection of the suspension at field strengths above 1 kV/mm. View Full-Text
Keywords: electrorheology; tungsten oxide; positive electrorheological effect; negative electrorheological effect; electroconvection electrorheology; tungsten oxide; positive electrorheological effect; negative electrorheological effect; electroconvection
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Agafonov, A.V.; Kraev, A.S.; Kusova, T.V.; Evdokimova, O.L.; Ivanova, O.S.; Baranchikov, A.E.; Shekunova, T.O.; Kozyukhin, S.A. Surfactant-Switched Positive/Negative Electrorheological Effect in Tungsten Oxide Suspensions. Molecules 2019, 24, 3348.

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