Interfacial Polarization and Electroresponsive Electrorheological Effect of Anionic and Cationic Poly(ionic liquids)

Abstract

Owing to weak ion pair electrostatic interaction and intrinsically hydrophobic nature, poly­(ionic liquids) (PILs) have potentiality as anhydrous polyelectrolyte-based electrorheological (ER) smart materials. Up to now, however, only cationic PILs as ER materials have been studied. In this work, we report the first ER materials based on anionic poly­[4-styrenesulfonyl­(trifluoromethylsulfonyl)­imide tetraethylammonium] (P­[STFSI]­[N2222]) and conduct a comparative study on electroresponsive ER effect with its cationic counterpart poly­[(p-vinylbenzyl)­triethylammonium trifluoromethanesulfonamide] (P­[VBTEA]­[TFSI]) having similar structure of component ions. It shows that the ER effect of anionic P­[STFSI]­[N2222] is sound but it is different from that of cationic P­[VBTEA]­[TFSI], though they have a similar structure of ions. At room temperature, the ER effect of P­[VBTEA]­[TFSI] is higher than that of P­[STFSI]­[N2222], while the power consumption of P­[STFSI]­[N2222] is lower than that of P­[VBTEA]­[TFSI] and the working-temperature region of P­[STFSI]­[N2222] is broader than that of P­[VBTEA]­[TFSI]. Dielectric spectroscopy study indicates that compared to P­[STFSI]­[N2222], the stronger ER effect of P­[VBTEA]­[TFSI] is because P­[VBTEA]­[TFSI] has larger intensity and faster rate in interfacial polarization than P­[STFSI]­[N2222]. Raman spectra and activation energy measurements demonstrate that the different polarization characteristics further originate from the fact that compared to N2222+ cation, TFSI– anion as mobile charge can contribute higher charge number and mobility due to its strong plasticization effect. But the plasticization effect also increases the segment relaxation of PILs and thus results in large ion leakage and a narrow working-temperature region of P­[VBTEA]­[TFSI]. This study extends the diversity scope of PILs for ER materials and gives an in-depth understanding about the influence of component ion structure on the interfacial polarization and the ER effect of PILs.

Preparation of Cellulose/Laponite Composite Particles and Their Enhanced Electrorheological Responses

“…It means the ER fluid without the stimuli of the electric field is more like a viscoelastic liquid. As mentioned above, after applying an electric field, the particles in ER fluids form chains or columns [ 47 , 48 ]. That is why G’ increases by several orders of magnitude and remains constant until strain amplitude reaches a certain value, which is the LVE region.…”

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

“…At relatively high temperatures, the relaxation peak appears and the peak position moves towards high frequency as the temperature rises. According to the analysis in our previous report [ 29 ], this relaxation process is attributed to the interfacial polarization induced by the movement and accumulation of dissociated PF 6 − at the interface between PIL particles and silicone oil. To get good ER property, it has required ER particles to have not only large interfacial polarizability but also suitable polarization rate because ERFs are usually work under the simultaneous stimuli of electric and shearing fields [ 28 ].…”

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

“…Due to the higher ion number density in the dual-cation PILs, it exhibits higher polarizability and stronger ER response under an electric field. In addition, to study the influence of the chemical structure of the counter cation on the ER effect of anionic PILs, Zhao et al [ 50 , 92 , 126 , 130 ] synthesized poly[4-styrenesulfonyl (trifluoromethylsulfonyl) imide (P[STFSI][X]) with anionic polymer backbone and cationic counterion. It is found that the size of cations did not show a monotonic influence on the ER effect of the PILs.…”

“…Marins et al reported ILs-assisted silica particles which presented higher permittivity and better ER effect than pure silica particles [ 45 , 46 , 47 ]. Yin et al have done a series of work on designing PILs-based ER materials with various chemical structures in cations and anions [ 48 , 49 , 50 ]. Even though ILs have shown excellent physicochemical properties in other fields, there are still several key issues to be solved when applied as ER materials.…”