Hybrid polyaniline-coated sepiolite nanofibers for electrorheological fluid applications

Abstract

Hybrid materials constituted by sepiolite covered with polyaniline (PAni) with different compositions have been prepared using two simple methods: bulk and slurry oxidative polymerization. The hybrid nanofibers were characterized by Fourier transform-infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), electrical conductivity, dielectric spectroscopy analysis and electrorheological response.Fiber-based nanocomposites with PAni nanoparticles well adhered to the sepiolite surface were successfully prepared by slurry polymerization. The best recovering of the nanofibers was observed in nanocomposites containing 46 wt% of PAni, (SP 50:50s sample) as indicated by FTIR and TEM and quantified by TGA analysis. Also the best electrorheological response was obtained with the corresponding suspensions containing 10 wt% of the hybrid material suspended in castor oil. The values of the field induced shear modulus in the linear viscoelastic region : G' = 536 kPa at E=2 kV/mm is higher than those found for the suspensions of pure components, PAni or sepiolite, and one of the best values obtained with conventional ER fluids. A model to estimate the interaction between two nanofibers has been proposed considering the length and thickness of the nanofiber, calculated by TEM.

Conducting polyaniline-wrapped sepiolite composite and its stimuli-response under applied electric fields

“…The PANI/SPL-based ER fluid possesses very strong solid-like behavior, which exhibits the dominating factor of an elastic property over the viscous one. On the other hand, without an electric field, G was similar to that of liquid-like behavior, in which G increases linearly with increasing frequency [28].…”

“…This composite was dispersed in silicone oil for ER fluid characterization, especially regarding a flow curve behavior and yield stress from a steady state test and stress relaxation from a dynamic oscillation test compared to previously reported work [28]. Their ER properties were found to exhibit improved flow behavior and yield properties.…”

“…Owing to the discontinuity of the silica sheets, silanol groups are present on the external surface of the silicate particles [26]. The large specific surface area and high porosity of SPL account for its remarkable adsorptive properties that make it a promising material for a wide range of applications [27] including ER fluid [28]. In particular, in the area of filler materials, SPL has already shown not only mechanical reinforcing capability in polymeric matrices, [29][30][31] but also improved rheological properties and thermal stability [32,33].…”

Synthesis and characterization of crosslinked chitosan immobilized on bentonite and its grafted products with polyaniline

“…The bands at 3697 and 3622 cm −1 , which are typical to hydroxyl group OH of bentonite, located inside the sheet appeared in CIB composites with same intensity and position indicating that chitosan was not intercalated into the silicate layer. At the same time, the band at 3429 cm −1 which is related to OH groups on the clay surface is shifted to lower frequency 3418 cm −1 , suggesting interfacial interaction between chitosan and bentonite surface, this is consistent with XRD results. However, as compared to the spectra of pristine chitosan, the frequency of vibration band at 1582 cm −1 , in the nanocomposite (CIB) which corresponds to the deformation vibration of protonated amine group, is shifted toward lower frequency values 1508 cm −1 .…”

Ionic liquid-based organically modified silica for the development of new electrorheological fluids

“…As an external electric field is applied, such particles become polarized and aligned along the electric field direction and can attract each other by strong dipole-dipole interactions. As a consequence, fibril-like structures are formed in the medium, thus contributing to a drastic change in the rheological properties of the ERF [3,4]. Due to these unique characteristics, ERFs are considered as smart materials and have been experienced a great interest in several engineering applications, such as damping devices, shock absorbers, torque transducers, as well as human muscle stimulators, etc.…”