Self-Healing Fire Prevention and Extinguishing Hydrogel Derived from Carboxymethyl Cellulose-Modified Amphiphilic Copolymers

Gel materials are widely used in underground mining for air leakage sealing and coal spontaneous combustion prevention. In this study, a novel self-healing carboxymethyl cellulose-modified amphiphilic polymer hydrogel with fire prevention and extinguishing capabilities is synthesized through ionic crosslinking between CMC-<i>graft</i>-poly(AM-<i>co</i>-NaA-<i>co</i>-BAM) and aluminum citrate (AlCit). The copolymer is constructed by grafting sodium carboxymethyl cellulose (CMC) onto an amphiphilic polymer backbone composed of acrylamide (AM), sodium acrylate (NaA), and N-benzylacrylamide (BAM), forming a dual-network structure via hydrophobic association and hydrogen bonding. The carboxymethyl cellulose-modified amphiphilic polymer demonstrates optimal viscosity-enhancing performance at a CMC content of 7.5 wt%. CMC-<i>graft</i>-poly(AM-<i>co</i>-NaA-<i>co</i>-BAM) demonstrated superior temperature, shear, and salt resistant performance compared with poly(AM-<i>co</i>-NaA-<i>co</i>-BAM), poly(AM-<i>co</i>-NaA), and CMC polymers, as well as enhanced viscoelasticity and self-healing capability. When crosslinked with AlCit, CMC-<i>graft</i>-poly(AM-<i>co</i>-NaA-<i>co</i>-BAM)-AlCit gel demonstrated superior viscoelastic properties and self-healing capability, as well as thermal stability, which gave the superior fire prevention and extinguishing performance for charcoal in fire extinction tests. CMC-<i>graft</i>-poly(AM-<i>co</i>-NaA-<i>co</i>-BAM) has abundant cross-linking sites, which lead to accelerated gelation and improved mechanical strength, while the hydrophobic microdomains acted as physical cross-linking points that interconnected polymer chains into a three-dimensional network. The hydrophobic interactions within the hydrogel are dynamically reversible. This intrinsic property allows physical cross-links to spontaneously reassociate when fracture surfaces make contact. Consequently, the material exhibits autonomous self-healing.