Stretchable, Low-Hysteresis, and Recyclable Ionogel by Ionic Liquid Catalyst and Mixed Ionic Liquid-Induced Phase Separation

Abstract

Stretchable ionogels are rapidly emerging as ideal materials for the construction of flexible ionotronics and soft machines. However, current ionogels suffer from low stretchability and large hysteresis, existing unstable signals at large deformations, and repetitive actions. Here, we propose a simple strategy based on mixed ionic liquid (IL)-induced phase separation to fabricate highly stretchable, tough, and low-hysteresis ionogels by dissolving poly-(vinyl alcohol) (PVA) in IL mixture of 1-allyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium ethyl sulfate. The crosslinking network microstructures with special nanophase separated domains endow the ionogel with a high stretchability (1030%) and toughness (0.21 MJ/m 3 ), which are 4.0 and 13.5 times that of the PVA ionogel synthesized in 1-allyl-3-methylimidazolium chloride with H 2 SO 4 . The low mechanical hysteresis characteristic of these ionogels is evidenced by cyclic tensile and compressive stress− strain curves. Moreover, the ultralow PVA content (3−8%) and typical sea-island microstructure endow the ionogel with superior room-temperature ionic conductivities (up to 1.8 mS/cm) and lower activation energies. Importantly, these ionogels show excellent recyclability and reprocessability due to the dissociation and recombination of the acetylated covalent cross-linking with the acidic IL catalyst. Potential applications of these resilient ionogels as flexible strain and pressure sensors for detecting the dynamic deformations under cyclic loading are further demonstrated.

Ionogels and eutectogels for stable and long-term EEG and EMG signal acquisition

“…The resultant ionogel displayed excellent elasticity (1030%) and high ionic conductivity (around 1.8 mS cm −1 ) with low hysteresis. The superior mechanical properties of the ionogel can be attributed to the presence of rigid regions rich in PVA and the presence of flexible regions rich in IL [40].…”

Strain-Induced Phase Separation and Mechanomodulation of Ionic Conduction in Anisotropic Nanocomposite Ionogels

“…On the other hand, phase separation, as a facile and efficient method, has been lately explored to fabricate mechanically strong and tough ionogels, which can form the hard polymer-rich reinforcement phase and promote interactions to dissipate energy, whereas the soft IL-rich phase will provide high ductility and reduce the stress concentration during deformation. − Furthermore, special phase-separated structures can also provide ionic channels and thereby enhance conductivity . Moreover, the phase separation-induced variation in ionic conductivity and mechanical strength of ionogels has been used to enhance the sensitivity of sensors .…”

Fluorine-Containing Ionogels with Stretchable, Solvent-Resistant, Wide Temperature Tolerance, and Transparent Properties for Ionic Conductors

“…For network construction, design ideas usually include dual network structures [18][19][20], interpenetrating networks [21][22][23], copolymer single-layer network structures [24][25][26], etc. The materials that make up the ionogel network are largely based on polyelectrolytes and hydrophilic polymers, such as polyvinyl alcohol [17,27,28], polyacrylic acid [29,30], and polyacrylamide [31,32]. Based on these strategies, ionogels have generally achieved high transparency and stretchability [8,33].…”