An important challenge in the field of electrorheology is identifying low-viscosity fluids that would exhibit significant changes in viscosity, or a yield stress, upon the application of an external electric field. Our recent research showed that optimal compositions of mixtures, 10 wt % sulfonated polyhedral oligomeric silsesquioxanes (s-POSS) mixed with polydimethyl siloxane (PDMS), exhibited significant electrorheological activity. Here we show that s-POSS/PDMS mixtures containing polystyrene (PS) fillers, of micrometer-sized dimensions, containing as little as ~1 wt % s-POSS, exhibited an increase in ER activity by an order of magnitude, beyond that of s-POSS/PDMS mixtures. The dynamic yield stress was found to scale with the particle diameter, a, as τ(y) is proportional to a(0.5) and with the electric field as τ(y) is proportional to E(1.5-2.5); this behavior is reasonably well understood within the context of dielectric electrorheological theory.

It is shown, for the first time, that mixtures of sulfonated polyhedral silsesquioxane cage structures (sPOSS) and poly(dimethyl siloxane) (PDMS) with silicone oil exhibit significant electrorheological (ER) activity. At low sPOSS concentrations, less than 10 wt %, the viscosity is enhanced by approximately 100, which is comparable to the viscosity enhancements exhibited by conventional ER fluids, under the influence of comparable applied electric fields, E = 2 kV/mm. Measurements of the shear stress, sigma, dependencies on E, the conductivities, and relative permittivities reveal that the properties of these POSS/PDMS systems cannot be reconciled with theory developed to explain the behavior of conventional ER fluids.

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Compression studies of electrorheological (ER) fluids have been impeded by not knowing the concentration of particles held between the plates. This study presents a technique that calls for using a constant volume setup that solves the problem. This study also includes results on how the concentration of particles and the viscosity of the dispersing oils affect the compression of an ER fluid. The conclusions of this study are that the constant volume squeeze flows of ER fluids are significantly different from what has been predicted with constant volume squeeze flow theories.

This article introduces a new electrorheological (ER) fluid. A molecular cage structure for electrorheological applications has been synthesized, and the ER behavior of the octa-functionalized polyhedral oligomeric silsesquioxane (POSS) variant in silicone oil (PDMS) has been shown. The hydrolyzation route has been used in the synthesis, the microstructure has been displayed using scanning electron microscopy, the yield has been ascertained, and the compound has been characterized. The rheological properties are demonstrated on the ER fluid through steady flow and oscillatory tests to investigate the effects of change in concentration on the functional group attached to the inorganic silicon–oxygen core structure of the POSS compound. The electrorheological efficiency was analyzed, and dielectric characterization was done. The flow curve was described by the Herschel–Bulkley model, and yield stress values were derived from the model. The octa-cyanoPOSS/PDMS electrorheological fluid has been shown to have ER activity.