Multifunctional tough ionogels enabled by microphase separation for reliable physiological sensing

A sequential network-construction strategy is proposed for fabricating tough ionogels with phase-organized microstructures by introducing a flexible poly(methyl acrylate) (PMA) network into a relatively stiff poly(cyclohexyl acrylate) (PCHA) network, followed by the incorporation of an ionic liquid. Differences in monomer-polymer affinity, together with monomer penetration and swelling of the preformed PCHA network and subsequent polymerization-induced compositional evolution, promote the formation of a microphase-separated, bicontinuous network structure. Within this phase-organized architecture, the interconnected polymer networks facilitate efficient load transfer and mechanical energy dissipation, while the compliant network components accommodate large deformations and maintain high stretchability. The combined effects of network interpenetration, chain entanglement, and intermolecular interactions therefore contribute to the enhanced mechanical robustness. As a result, the resulting ionogels display outstanding mechanical performance, including a high fracture strength of ∼21.3 MPa, an exceptional toughness of ∼3500 J m^-2, and a Young's modulus of ∼6.5 MPa. Notably, the evolution of the bicontinuous phase under large deformation is clearly revealed by in situ small-angle X-ray scattering (SAXS) analysis in conjunction with coarse-grained simulations of network evolution dynamics. Ionogels prepared through polymer chains entanglement exhibit outstanding fatigue resistance, as evidenced by a residual strain of only ∼1% after 100 loading-unloading cycles over a strain range of 0-12%, together with rapid recovery to their original configuration within 5 s. Our results suggest that appropriately tuning monomer-polymer affinity, monomer penetration and swelling, and polymerization-induced compositional evolution may provide a viable route for constructing bicontinuous network structures in hybrid polymer/ionic-liquid systems.