A disulfonic acid functionalized ionic liquid, 1,3-disulfonic acid imidazolium chloride ([Dsim]Cl), was synthesized and utilized to prepare TiO 2 -based ionogel nanoparticles (TiO 2 -[Dsim]Cl) using a precipitation method. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy showed that the [Dsim]Cl molecules were introduced into the TiO 2 matrix through electrostatic force between [Dsim]Cl and Ti atoms. The EDS mapping analysis indicated that the elements of [Dsim]Cl were distributed inside and on the surface of the TiO 2 -[Dsim]Cl nanoparticles. The electrorheological (ER) properties of TiO 2 -[Dsim]Cl ionogel nanoparticles and pure TiO 2 were evaluated under the same conditions. The ER properties of the TiO 2 -[Dsim]Cl nanoparticles were found to be closely related to the content of [Dsim]Cl. Dielectric analysis demonstrated that adding an appropriate amount of [Dsim]Cl can enable the TiO 2 nanoparticles to have a higher polarizability and a suitable relaxation time, both of which can significantly enhance the ER effect of the TiO 2 -[Dsim]Cl nanoparticles. More significantly, the TiO 2 -[Dsim]Cl nanoparticles exhibited a stable yield stress over a wide temperature range from 5 °C to 85 °C, indicating the high thermal stability of the TiO 2 -[Dsim]Cl ionogel nanoparticles.

Cellulose, as a natural polymer with an abundant source, has been widely used in many fields including the electric field responsive medium that we are interested in. In this work, cellulose micron particles were applied as an electrorheological (ER) material. Because of the low ER effect of the raw cellulose, a composite particle of cellulose and Laponite was prepared via a dissolution–regeneration process. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were used to observe the morphologies and structures of the composite particles, which were different from pristine cellulose and Laponite, respectively. The ER performances of raw cellulose and the prepared composite were measured by an Anton Paar rotational rheometer. It was found that the ER properties of the composite were more superior to those of raw cellulose due to the flake-like shapes of the composite particles with rough surface. Moreover, the sedimentation stability of composite improves drastically, which means better suspension stability.

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Ionic liquids (ILs) are a class of pure ions with melting points lower than 100 °C. They are getting more and more attention because of their high thermal stability, high ionic conductivity and dielectric properties. The unique dielectric properties aroused by the ion motion of ILs makes ILs-contained inorganics or organics responsive to electric field and have great application potential in smart electrorheological (ER) fluids which can be used as the electro-mechanical interface in engineering devices. In this review, we summarized the recent work of various kinds of ILs-contained inorganic ionogels and poly(ionic liquid)s (PILs) as ER materials including their synthesis methods, ER responses and dielectric analysis. The aim of this work is to highlight the advantage of ILs in the synthesis of dielectric materials and their effects in improving ER responses of the materials in a wide temperature range. It is expected to provide valuable suggestions for the development of ILs-contained inorganics and PILs as electric field responsive materials.

A stretchable double-network (DN) ionogel composed of a physically crosslinked network of chitosan (CS) and a chemically crosslinked network of polyacrylic acid (PAA) was prepared in an ionic liquid ([EMIM][OAc]) using a one-step polymerization method. In this ionogel (CS/PAA), the CS and the PAA polymer chains served as backbones, which constructed an interpenetrating DN structure via numerous hydrogen bonds formed through the hydroxyl, amino and carboxyl groups on the polymer chains. The DN structure improves the mechanical properties of the ionogel. Therefore, the CS/PAA DN ionogel exhibited outstanding mechanical performance in many ways: tensile strength up to 2.04 MPa, strain range up to 1046% and the value of toughness up to 8.52 MJ/m3. The ionogel also showed good self-recovery performance, fatigue resistance, ability to work in a broad temperature range (−20~80 °C) and adhesion properties. As a flexible sensor, the CS/PAA DN ionogel showed high strain sensitivity (gauge factor = 6.235). It can sensitively detect human motion (such as joint-bending, vocal fold vibration, walking gait and other human body motions), revealing the practical application potential of flexible electronic devices.