The Effect of Dielectric Polarization Rate Difference of Filler and Matrix on the Electrorheological Responses of Poly(ionic liquid)/Polyaniline Composite Particles

Abstract

By using different conductivity of polyaniline as filler, a kind of poly(ionic liquid)/polyaniline composite particles was synthesized to investigate the influence of dielectric polarization rate difference between filler and matrix on the electrorheological response and flow stability of composite-based electrorheological fluids under simultaneous effect of shear and electric fields. The composite particles were prepared by a post ion-exchange procedure and then treated by ammonia or hydrazine to obtain different conductivity of polyaniline. Their electrorheological response was measured by dispersing these composite particles in insulating carrier liquid under electric fields. It showed that the composite particles treated by ammonia had the strongest electrorheological response and most stable flow behavior in a broad shear rate region from 0.5 s−1 to 1000 s−1. By using dielectric spectroscopy, it found that the enhanced electrorheological response with stable flow depended on the matching degree of the dielectric polarization rates between poly(ionic liquid) matrix and polyaniline filler. The closer their polarization rates are, the more stable the flow curves are. These results are helpful to design optimal composite-based electrorheological materials with enhanced and stable ER performance.

Electrorheological Fluids of GO/Graphene-Based Nanoplates

“…As a result, the ER effect of composite nanoplates can be optimized. It provides a new strategy for developing high-performance composite ER materials with controllable electrical properties and proficient ER effect [ 86 , 87 ].…”

The Electric Field Responses of Inorganic Ionogels and Poly(ionic liquid)s

“…The change of surface potential makes the composites behave stronger ER response under the electric field and the yield stress obtained under an electric field of 4 kV/mm is about 2.3 kPa, which is twice that of pure PILs and 2.5 times that of PANI. In order to study the effect of reducing ion leakage and the degree of polarization matching between PANI and PILs, PANI was treated by alkali to obtain different forms [ 110 , 139 ]. After PANI undergoing different treatments, PILs/PANI (NH 3 ) particles exhibit a stable shear range at room temperature, while PILs/PANI (N 2 H 4 ) particles have stable shear at high temperatures.…”

“…To fit the dielectric data of ER materials, a relaxation Equation, which includes a Cole-Cole’s term, a DC conductivity term and an electrode polarization (EP) term, was used to analyze the dielectric spectra [ 139 ]: where is the dielectric strength ( and are the limit values of the relative permittivity at the frequencies below and above the relaxation frequencies, respectively), λ = 1/ ω max the relaxation time, ω max is the local angular frequency of dielectric loss peak, β is the Cole-Cole parameter indicating the distribution of the relaxation time, σ is the DC conductivity, n is related to the slope of EP’s high frequency tail, and A is related to the amplitude of EP.…”

“…If the dispersed phase of ER fluid consists of two components, two Cole-Cole’s terms can be used to analyze the dielectric properties. The equations of ε ′ and ε ″ are shown below, where subscript 1 and 2 are for each component respectively [ 139 ]. …”

“…It means temperature affects the migration of ions in ILs or PILs which is related to the relaxation time. It is found that the reciprocal of the dielectric relaxation time ( λ −1 ) follows the Arrhenius equation [ 139 ]: where E a is the activation energy, R is the molar gas constant, and T is the absolute temperature. Upon the study of the Arrhenius dependence of the PILs-based ER fluids, it is indicated that the ion motions in PILs or its composites are from the thermal diffusion, and not coupled with the chain segment below T g of the PILs.…”