Influence of Tethered Ions on Electric Polarization and Electrorheological Property of Polymerized Ionic Liquids

Abstract

Polymerized ionic liquids (PILs) show potential to be used as new water-free polyelectrolyte-based electrorheological (ER) material. To direct ER material design at the molecular level, unveiling structure-property relationships is essential. While a few studies compare the mobile ions in PILs there is still a limited understanding of how the structure of tethered counterions on backbone influences ER property. In this study, three PILs with same mobile anions but different tethered countercations (e.g., poly(dimethyldiallylammonium) P[DADMA]+, poly(benzylethyl) trimethylammonium P[VBTMA]+, and poly(1-ethyl-4-vinylimidazolium hexafluorophosphate) P[C2VIm]+) are prepared and the influence of tethered countercations on the ER property of PILs is investigated. It shows that among these PILs, P[DADMA]+ PILs have the strongest ER property and P[C2VIm]+ PILs have the weakest one. By combining dielectric spectra analysis with DFT calculation and activation energy measurement, it can clarify that the influence of tethered counterions on ER property is mainly associated with ion-pair interaction energy that is affecting ionic conductivity and interfacial polarization induced by ion motion. P[DADMA]+ has the smallest ion-pair interaction energy with mobile ions, which can result in the highest ionic conductivity and the fastest interfacial polarization rate for its strongest ER property.

Efficient and stable electrorheological fluids based on chestnut-like cobalt hydroxide coupled with surface-functionalized carbon dots

“…16 In particular, for a polar molecular ERF, 17 although it has higher mechanical properties, the existence of polar molecules on the surface of the dispersed phase leads to an ERF with poor thermal stability and large leakage current density. 18 To solve this problem, some researchers have used intrinsically polarizable materials, 19 such as conductive polymers, [20][21][22][23] carbon nanotubes, 24,25 graphene oxide (GO), 26 and poly(ionic liquids), [27][28][29][30] to develop a variety of ERFs. But the low yield stress or large zerofield viscosity of these ERFs limits their practical applications.…”

A Water-Free Ionic Covalent Organic Polymer with High Electrorheological Activity and Temperature Stability

“…We consider that this may be due to the fact that although the activation energy ( E a = E c + E el , as shown in Figure ) of ion dissociation and migration in iCOP-TFSI particles is low, the energy barrier of ions through the interface between particles and carrier liquid (Δ E = E a1 – E a , where E a1 is the activation energy (90.6 kJ/mol) of ion diffusion in the whole ER fluid, which is calculated by the dc conductivity ( σ dc ) of iCOP-TFSI ER fluid as a function of temperature with the Arrhenius equation σ dc ∝ e – E a1/ RT ) is relatively high as shown in Figure h. Figure shows that iCOP-TFSI has a larger Δ E (24.0 kJ/mol) and smaller E a (66.6 kJ/mol) than those (Δ E = 13.6 kJ/mol and E a = 70.53 kJ/mol) of linear D-PIL­[TFSI] . This means that the iCOP structure enables the internal counterions to have easy dissociation and migration ability in the particles, while the cage covalent organic framework structure effectively limits the long-range migration of TFSI – from iCOP particles into carrier liquid.…”

“…Figure 6 shows that iCOP-TFSI has a larger ΔE (24.0 kJ/mol) and smaller E a (66.6 kJ/mol) than those (ΔE = 13.6 kJ/mol and E a = 70.53 kJ/mol) of linear D-PIL [TFSI]. 53 This means that the iCOP structure enables the internal counterions to have easy dissociation and migration ability in the particles, while the cage covalent organic framework structure effectively limits the long-range migration of TFSI − from iCOP particles into carrier liquid. Therefore, the iCOP-TFSI ER fluid shows very low leaking current density.…”

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

“…The size of cation and the interaction between anions will affect the conductivity of ILs and PILs [ 127 , 128 ]. In order to explore the effect of cations on the ER response of PILs, He et al [ 129 ] synthesized PILs with different tethered cations dimethyldiallylammonium ([DADMA] + ), benzylethyl trimethylammonium ([VBTMA] + ) and 1-vinyl 4-ethylimidazolium ([C2VIm] + ) and the same counter anion hexafluorophosphate (PF 6 − ). The chemical structures of the cations are shown in Figure 4 .…”