One-step synthesis of intelligent ionohydrogels toughened with carboxyl-Al3+ coordination facilitated by ionic liquids

Conductive hydrogels are promising materials as flexible electronics, and metal coordination is widely used to prepare tough and conductive hydrogels. While, some metal ions, e.g., Al3+ is highly hydrated in hydrogels, which cannot form effective coordination cross-links to strengthen hydrogels. Herein, by introducing hydrophilic ionic liquids ([EMIM]OAc) to disrupt the hydration state of Al3+, the formation of coordination between Al3+ and carboxyl groups in PAA chains is facilitated. Through a one-step in situ free-radical polymerization, tough VSNPs-PAA-Al3+ ionohydrogels are facilely prepared, which are dually cross-linked by multivalent VSNPs and carboxyl-Al3+ coordination cross-links. The obtained ionohydrogels show high toughness of 27.3 MJ m−3, with tensile strength of 4280 kPa and large elongation at break of 1360%. Moreover, due to the existence of numerous mobile ions, the VSNPs-PAA-Al3+ ionohydrogels possess superior conductivity of 1.60 S m−1 and high strain sensitivity with GF of 9.83, which are potential candidates as wearable strain sensors.