Lignin-Derived hydrogel exhibiting underwater self-healing under harsh reservoir conditions

In this study, a self-healing lignin-based polyacrylamide/polyvinyl alcohol (SL-cPAM/PVA) hydrogel featuring excellent high temperature and salt resistance was successfully synthesized via a two-step method. Sodium lignosulfonate (S-Lignin) was first incorporated into a chemically crosslinked polyacrylamide (cPAM) network, followed by the formation of dynamic boronate ester linkages among polyvinyl alcohol (PVA), catechol groups, and borax to construct a dual crosslinked structure. The rheological, thermal, and mechanical properties of the hydrogel were comprehensively characterized. The results indicate that the introduction of S-Lignin improved the initial decomposition temperature from 150 °C to 178 °C, and enabled the hydrogel to achieve self-healing behavior at 130 °C, supported by reversible borate ester bonds, hydrogen bonding, and ionic interactions. The hydrogel maintained structural integrity in high-salinity environments (up to 21 × 10 4 mg/L) and demonstrated remarkable recovery in mechanical strength and microstructure after damage. Even after 30 days of thermal aging at 130 °C, brine-healed hydrogel remained intact without signs of hydrolysis. These findings indicate the excellent potential of SL-cPAM/PVA hydrogel as a water-plugging material in high-temperature, high-salinity oilfield environments, providing a sustainable and functional approach for enhanced oil recovery.