High-strength, tough, and self-healing hydrogel based on carboxymethyl cellulose

Hydrogels are the focus of extensive research due to their potential applications in various fields including tissue engineering, drug delivery, soft actuators, and sensors, etc. However, insufficient functionality and weak mechanical properties limit their practical applications. Herein, we developed a simple approach to fabricate strong, tough and self-healable hydrogels by introducing sodium carboxymethyl cellulose (CMC) into poly (acrylic acid) (PAA)–Fe³⁺ hydrogels as well as by simply soaking the gels in sodium chloride (NaCl) solution. During the deformation process, the synergetic interactions of –COO⁻/Fe³⁺ physically ionic networks as well as PAA covalent networks can homogeneously distribute stress, and more importantly, high degree of network densities, and chain entanglements introduced by soaking treatment could act as “sacrificial bonds” to dissipate energy effectively. As a result, the resulting optimal PAA/CMC_1.0–Fe³⁺–S samples with water content of approximately 37.7 wt% possessed remarkable mechanical properties, with elastic modulus of 0.41 MPa, fracture tensile stress of 4.42 MPa, superior to that of PAA–Fe³⁺ and PAA/CMC_1.0–Fe³⁺ hydrogels. Additionally, the noncovalent ionic interactions of PAA/CMC_1.0–Fe³⁺ hydrogels serve as dynamic but stable associations, leading to effective self-healing efficiency (over 85%) after damage, with recovered fracture stress of 3.75 MPa as well as an elongation at break of about 750%. We expect this facile strategy may enrich the avenue in exploration of high-strength, tough and self-healing cellulosic hydrogels.