Yan Cheng,Hongnan Zhu,Shuaijie Li,Min Xu,Tianci Li,Xuemeng Yang,Hongzan Song
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 cross-linking network microstructures with special nanophase separated domains endow the ionogel with a high stretchability (1030%) and toughness (0.21 MJ/m3), which are 4.0 and 13.5 times that of the PVA ionogel synthesized in 1-allyl-3-methylimidazolium chloride with H2SO4. 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.
The reinforcement of rubbers by nanoparticles is always accompanied with enhanced dissipation of mechanical energy upon large deformations. Methods for solving the contradiction between improving reinforcement and reducing energy dissipation for rubber nanocomposites have not been well developed. Herein carbon black (CB) filled isoprene rubber (IR)/liquid isoprene rubber (LR) blend nanocomposites with similar crosslink density ( v e ) are prepared and influence of LR on the strain softening behaviors including Payne effect under large amplitude shear deformation and Mullins effect under cyclic uniaxial deformation is investigated. The introduction of LR could improve the frequency sensitivity of loss modulus and reduce critical strain amplitude for Payne effect and loss modulus at the low amplitudes. Meanwhile, tuning v e and LR content allows reducing mechanical hysteresis in Mullins effect without significant impact on the mechanical performances. The investigation is illuminating for manufacturing nanocomposite vulcanizates with balanced mechanical hysteresis and reinforcement effect.
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