Low‐Hysteresis and High‐Toughness Hydrogels Regulated by Porous Cationic Polymers: the Effect of Counteranions

Abstract Service life and range of polymer materials is heavily reliant on their elasticity and mechanical stability under long‐term loading. Slippage of chain segments under load leads to significant hysteresis of the hydrogels, limiting its repeatability and mechanical stability. Achieving the desired elasticity exceeding that of rubber is a great challenge for hydrogels, particularly when subjected to large deformations. Here, low‐hysteresis and high‐toughness hydrogels were developed through controllable interactions of porous cationic polymers (PCPs) with adjustable counteranions, including reversible bonding of PCP frameworks/polymer segments (polyacrylamide, PAAm) and counteranions/PAAm. This strategy reduces chain segment slippage under load, endowing the PCP‐based hydrogels (PCP‐gels) with good elasticity under large deformations (7 % hysteresis at a strain ratio of 40). Furthermore, due to the enlarged chain segments entanglement by PCP, the PCP‐gels exhibit large strain (13000 %), significantly enhanced toughness (68 MJ m −3 ), high fracture energy (43.1 kJ m −2 ), and fatigue resistance. The unique properties of these elastic PCP‐gels have promising applications in the field of flexible sensors.