Dielectric Polarization and Electrorheological Response of Poly(ethylaniline)-Coated Reduced Graphene Oxide Nanoflakes with Different Reduction Degrees.

Yudong Wang,Honggang Chen,Jianbo Yin,Min Yang,Xiaopeng Zhao

doi:10.3390/polym12112528

Abstract

We prepared poly(ethylaniline)-coated graphene oxide nanoflakes and then treated them with different concentrations of hydrazine solution to form dielectric composite nanoflakes having different reduction degrees of reduced graphene oxide core and insulating polyethylaniline shell (PEANI/rGO). The morphology of PEANI/rGO was observed by scanning electron microscopy, while the chemical structure was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectrometer. The influence of reduction degrees on the conductivity, dielectric polarization and electrorheological effect of PEANI/rGO in suspensions was investigated by dielectric spectroscopy and rheological test under electric fields. It shows that the PEANI/rGO has two interfacial polarization processes respectively due to rGO core and PEANI shell. As the number of hydrazine increases, the conductivity and polarization rate of rGO core increase. As a result, the difference between the polarization rate of rGO core and that of the PEANI shell gradually becomes large. This increased difference does not significantly decrease the yield stress but causes the flow instability of PEANI/GO suspensions under the simultaneous action of electric and shear fields.

Highlights

Electrorheological fluids (ERFs) are a type of electrically responsive suspensions composed of dielectric particles in non-conducting carrier liquid [1,2]
It is seen that the polyethylaniline obtained by reduction with (PEANI)/reduced graphene oxide (rGO) samples have the same flake shape and size as PEANI/graphene oxide (GO), indicating that the hydrazine reduction does not destroy the flake structure and shape
This may be attributed to the fact that in PEANI/GO composites, the GO core is no longer a stacked structure but is a single or few-layer GO that will not be further disintegrated during reduction

Summary

Introduction

Electrorheological fluids (ERFs) are a type of electrically responsive suspensions composed of dielectric particles in non-conducting carrier liquid [1,2]. When an electric field is applied, the particles are polarized due to the difference between the dielectric constant of the carrier liquid and that of particles and, the particles aggregate into chains between two electrodes. These gap-spanning chains can distinctly increase the apparent viscosity of ERFs by several orders of magnitude and even make ERFs a gel-like solid under the effects of an electric fields of the order of kV/mm. This viscosity change or liquid–solid transformation is rapid and reversible. ERFs attract significant attention in many technical applications, such as dampers, microfluidics, robotics, transmissions, and soft actuators [3,4,5,6]

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