A synergistic flexibility management strategy for self-healing carboxymethyl cellulose hydrogel with strain responsiveness based on p-phenylenediamine

Ionic hydrogels, with adjustable physical and chemical properties, have been widely developed in the field of flexible sensing. The structural and functional integrity of ionic hydrogels under operational conditions is essential for their long-term stability and practical applicability. Herein, a rigid-flexible coupling crosslinking strategy was proposed, where p-phenylenediamine and urea served as complementary crosslinkers (rigid and flexible, respectively) within a carboxymethyl cellulose-based network. The rigid flexible coupling crosslinking network was constructed by a simple one-step method, enabling tunable flexibility through adjusting crosslinker ratios. This strategy not only enhanced the crosslinking density (tensile strength: 55.56 kPa) but retained the mobility of the polymer chain, endowing the hydrogel with the self-healing efficiency up to 90.41 % after 16 h and robust adhesion (221.69 kPa on aluminum). The noncovalent interactions based on aromatic rings (from benzene rings) and hydrogen bonding (from p-phenylenediamine) further contributed to these multifunctional properties. Additionally, the hydrogel exhibited high ionic conductivity (3.14 S/m) with high sensitivity (GF = 2.87 (50-200 %)) and rapid strain-responsive behavior (280 ms response and 260 ms recovery times), allowing accurate detection from subtle to large-scale body movements. These integrated advantages positioned the hydrogel as a promising candidate in the field of flexible sensing.