Electrorheology of Polystyrene Filler/Polyhedral Silsesquioxane Suspensions

Abstract

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.

Magnetite–polypyrrole core–shell structured microspheres and their dual stimuli-response under electric and magnetic fields

“…Under an applied electric field, the particles are polarized due to dielectric constant mismatch between the particles and medium. 19,20 The ER performance is known to be related to the particle shape, size and dielectric properties. [8][9][10][11] Many conducting polymers, such as polyaniline (PANI) and polypyrrole (PPy), exhibit ER behaviours when they are dedoped in a semi-conducting regime from 10 À5 S cm À1 to 10 À9 S cm À1 .…”

Core-Shell Structured Electro- and Magneto-Responsive Materials: Fabrication and Characteristics

“…The interfacial adsorption of a layer of dipolar molecules onto the surface of PS particles in a PDMS medium changed a previously ER inert suspension (PS/PDMS) to a viable ER fluid: s-POSS/PS/PDMS. In the subsequent study, they showed that by adding small concentrations (less than 2 wt%) of s-POSS to the ER fluid, sulfonated-PS (s-PS)/PDMS, resulted in the formation of a superior ER suspension, s-POSS/s-PS/PDMS, exhibiting a significant improvement in ER activity of over 200% at moderate fields [41]. This behavior was not readily rationalized in terms of current ER theories, which suggests that the properties of the shell, dielectric and conductive, largely determine the yield stress of the system.…”

Yield stress analysis of electrorheological suspensions containing core–shell structured anisotropic poly(methyl methacrylate) microparticles

“…Electrorheological (ER) fluids are suspensions of polarizable particles dispersed in insulating medium oils. Under the applied electric fields, the colloidal particles instantly attract one another to form solidlike networks along the direction of an applied electric fields . When the electric field is off, the aggregates are reversibly dispersed.…”

“…To be electrorheologically active, the suspended particle should be polarized under the electric field. For non‐polarizable or weakly polarizable particles such as polymer particles or silica microspheres, coating on the surfaces of the particles with a more polarizable or conducting materials can be a useful strategy . The core–shell type particles can get higher permittivity component compared to the insulating medium.…”