Zwitterionic Microgel-Reinforced Hydrogels with Low Hysteresis and High Toughness for Electrochemical Applications

Hydrogels are widely used in flexible sensors and energy devices due to their excellent flexibility, conductivity, and biocompatibility. However, achieving a hydrogel design that simultaneously offers high toughness, low hysteresis, and outstanding electrochemical performance remains a significant challenge. Herein, zwitterionic microgels with a special chemical design were synthesized from monomer 3-(1-(4-vinylbenzyl)-1<i>H</i>-benzo[<i>d</i>]imidazol-3-ium-3-yl)propane-1-sulfonate (VBIPS), which were further incorporated into a highly entangled polyacrylamide (PAM) network to fabricate a tough, low-hysteresis hydrogel. The penetrated pVBIPS microgels acted as cross-linking domains, promoting toughness through efficient stress transmission and crack resistance with restricted energy dissipation. The obtained PAM/pVBIPS hydrogel showed high toughness (1450.8 kJ/m³) with no significant degradation in mechanics after loading 100 cycles at 100% strain. Besides, due to the zwitterionic nature of pVBIPS domains, the PAM/pVBIPS-ZnSO₄ hydrogel showed good conductivity (52.9 mS cm^-1) and exhibited excellent sensitivity (GF = 4.48) when applied as a strain sensor. Additionally, it demonstrates good electrochemical stability when applied in a zinc-ion hybrid capacitor, retaining ∼92.23% capacitance after 24 h in static conditions. These results collectively highlight the pivotal role of zwitterionic microgels in reinforcing the mechanical integrity and electrochemical functionality of the conventional PAM hydrogels.