Victoria V. Kovaleva

A method for forming highly porous poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) composite particles with an excess nonconductive PSS component via spraying into liquid nitrogen, followed by freeze-drying, was proposed. The additional PSS content both compensates for the excess charge of PEDOT and acts as a binder during the formation of a highly porous network. Electrorheological fluids, i.e., dispersions of highly porous particles in silicone oil, were obtained. PEDOT:PSS/PSS composite particles with various component ratios were considered as fillers. Operating ranges of electric field strength and the most promising composite fillers were determined. The electrorheological activity of PSS particles was revealed for the first time. The activation effect of a small amount of PEDOT in the porous particles on the electrorheological behavior of the fluids was established. The intensity of the electrorheological effect depends on the particles’ composition and the electrical properties of the fluids. The possibility of developing electrorheological fluids with tunable properties by varying the composition of PEDOT:PSS-based composite filler particles was demonstrated.

Low-filled (1 wt%) electrorheological fluids of highly porous composite microparticles of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate/polyacrylamide in silicone oil were prepared. The prospects of electrorheological fluids developing with particles of the specified composition was demonstrated. Operating ranges of electric field strength were determined. For the first time, electrorheological fluids have been obtained with the response induced by poly(3,4-ethylenedioxythiophene) entirely. The results open up prospects for the creation of novel electrorheological fluids with hybrid fillers.

A chemical modification of cellulose diacetate by phthalate and nitrate was performed to increase solubility in organic solvents and change the electrical properties. The role of substituents on the conductivity, permittivity, and polarizability of cellulose films is revealed. It has been shown that highly porous micro particles can be obtained from cellulose derivatives by a simple and technological freeze‐drying method. The resulting micro sized aerogels have a predominantly spherical morphology and amorphous structure. Suspensions of porous particles of nitro‐ and phthalylated cellulose derivatives in silicone oil have an increased dielectric permittivity compared to cellulose diacetate particles. Produced particles are novel promising material with tunable electrical properties for advanced applications in composites, including for electrorheological fluids.

Effect of in situ formed silver nanoparticles doping on electrorheological response of highly porous chitosan particles in suspensions of polydimethylsiloxane (silicone oil) is considered. Silver nanoparticles are directly reduced by chitosan from solution. Highly porous chitosan particles with different silver content are fabricated by spraying from solution followed by freeze‐drying. A high and stable electrorheological response of suspensions in wide range of electric field strength is observed at a very low filler content of 1 wt%. The nature of the electrorheological effect is considered from the standpoint of dielectric spectroscopy. The activation energies of polarization processes are determined from the temperature dependences of the dielectric loss modulus. The study shows the opportunity to control the properties of stimuli‐responsive materials by changing the structure and physicochemical properties of the functional filler. This approach opens up new possibilities for creating materials with high performance and predetermined properties.