Electrorheology of aniline oligomers

Aniline oligomers were prepared by the oxidation of aniline with p-benzoquinone in aqueous solutions of methanesulfonic acid (MSA) of various concentrations. Their molecular structures were assessed by Fourier transform infrared spectroscopy. The electrorheological (ER) behavior of their silicone oil suspensions under applied electric field has been investigated. Shear stress at a low shear rate, τ 0.9, was used as a criterion of the rigidity of internal structures created by the application of an electric field. It was established from the fitting of the dielectric spectra of the suspensions with the Havriliak-Negami model that dielectric relaxation strength, as a degree of polarization induced by an external field contributing to the enhanced ER effect, increases and relaxation time, i.e., the response of the particle to the application of the field, decreases when a higher molar concentration of MSA is used. The best values were observed for suspensions of the sample prepared in the presence of 0.5 M of MSA. This suspension creates stiff internal structures under an applied electric field strength of 2 kV mm-1 with τ 0.9 of nearly 50 Pa, which is even slightly of higher value than that obtained for standard polyaniline base ER suspension measured at the same conditions. The concentration of the MSA used in the preparation of oligomers seems to be a crucial factor influencing the conductivity, dielectric properties and, consequently, rheological behavior, and finally ER activity of their suspensions. © 2013 Springer-Verlag Berlin Heidelberg

The electrorheological behavior of suspensions based on molten-salt synthesized lithium titanate nanoparticles and their core-shell titanate/urea analogues

This paper concerns the preparation of novel electrorheological (ER) materials using microwave-assisted synthesis as well as utilizing a suitable shell-providing system with enhanced ER performance. Lithium titanate nanoparticles were successfully synthesized, and their composition was confirmed via X-ray diffraction. Rheological properties were investigated in the absence as well as in the presence of an external electric field. Dielectric properties clarified the response of the particles to the application of an electric field. The urea-coated lithium titanate nanoparticle-based suspension exhibits higher ER performance in comparison to suspensions based on bare particles.European Regional Development Fund (ERDF); national budget of the Czech Republic within the framework of the project of the Centre of Polymer Systems [CZ.1.05/2.1.00/03.0111]; TBU in Zlin [IGA/FT/2013/014