Enhanced electrorheological activity of porous chitosan particles

[Display omitted] •Suspensions of polydimethylsiloxane filled by porous chitosan particles exhibit high electrorheological activity.•The porosity of the filler allows achieving higher yield stress at lower content of chitosan.•The porosity of the filler significantly enhances the sedimentation stability of suspensions.•Electrorheological fluids filled by porous chitosan particles well operate in on/off electric field mode. Novel porous filler for electrorheological fluids was fabricated from chitosan via freeze drying technique. An exceptional electrorheological effect was discovered in suspensions of polydimethylsiloxane (silicone oil) filled by highly porous chitosan particles. The electrorheological activity was studied by rotational rheometry and visualized by optical microscopy. High porosity of the filler allows preparing highly efficient electrorheological fluids at rather low (< 1 wt%) concentration of dispersed phase. The mechanism of chain-like structure formation was considered. The electrorheological behavior of suspensions and the filler structural organization at different concentration were comprehended in terms of dielectric properties. The rheological data were approximated by Bingham and Cho-Choi-Jhon equations. The sedimentation stability of chitosan suspensions in polydimethylsiloxane was significantly affected by particles porosity.