Inorganic/Organic Double‐Network Gels Containing Ionic Liquids

Abstract

Highly robust ion gels, termed double-network (DN) ion gels, composed of inorganic/organic interpenetrating networks and a large amount of ionic liquids (ILs), are fabricated. The DN ion gels with an 80 wt% IL content show extraordinarily high mechanical strength: more than 28 MPa of compressive fracture stress. In the DN ion gel preparation, a brittle inorganic network of physically bonded silica nanoparticles and a ductile organic network of polydimethylacrylamide (PDMAAm) are formed in the IL. Because of the different reaction mechanisms of the inorganic/organic networks, the DN ion gels can be formed by an easy and free-shapeable one-pot synthesis. They can be prepared in a controllable manner by manipulating the formation order of the inorganic and organic networks via not only multistep but also single-step processes. When silica particles form a network prior to the PDMAAm network formation, DN ion gels can be prepared. The brittle silica particle network in the DN ion gel, serving as sacrificial bonds, easily ruptures under loading to dissipate energy, while the ductile PDMAAm network maintains the shape of the material by the rubber elasticity. Given the reversible physical bonding between the silica particles, the DN ion gels exhibit a significant degree of self-recovery by annealing.

Highly Tough, Li‐Metal Compatible Organic–Inorganic Double‐Network Solvate Ionogel

“…Representative mechanical properties of SIGE and EGPE were determined by stress–strain measurements. As shown in Figure 1 a, the yield strength of SIGE reaches 3.7 MPa, which is several times higher than that of the reported DN ionogels . More importantly, no distinct stress–strain yield point was observed, and the modulus values are relatively low (less than 0.2 MPa).…”

“…The primary network of silica was physically crosslinked. During the tensile test, silica clusters tend to be disrupted to dissipate the loading energy, thus improving the mechanical strength . This might account for the distinct yield phenomenon (Figure a) for both SIGE and EGPE.…”

“…The previous efforts on DN gels are mainly focused on the hydrogel, but the reports on ionogels are few. Recently, Kamio et al synthesized a series of organic–inorganic DN ionogels with excellent mechanical strength, and the relationship between the performance and the reaction kinetics was elaborately discussed . Ding and co‐workers successfully fabricated a poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS)‐based DN ionogel with high ionic conductivity and good mechanical strength for flexible skin sensors, which are able to work in a wide temperature scope from −70 to 100 °C .…”

Self‐Healing Micellar Ion Gels Based on Multiple Hydrogen Bonding

“…To overcome this problem, many researchers have been attempting to fabricate tough hydrogels and organogels over the past few decades . Very recently, these concepts have been also applied to ion gels . Furthermore, inspired by living organisms, the concept of self‐healing has emerged and attracted ever‐increasing levels of attention in the development of highly durable and sustainable soft materials .…”

Ionic Tactile Sensors for Emerging Human‐Interactive Technologies: A Review of Recent Progress

“…For example, conventional crosslinked polyacrylamide hydrogels have low mechanical properties, limited stretchability, which leads to unfavorable feature to 3D curved and dynamic surfaces . Novel strategies including double‐networks, nanocomposites, dynamic cross‐linking have been developed to synthesize novel hydrogels with improved mechanical properties and even with self‐healing capabilities. The double network hydrogels can be stretched to over 2000% with a fractural energy of 9000 J m −2 .…”