Frontal curing of aluminosilicate–epoxy composites for extreme underwater environments

Rapid underwater repair using durable materials capable of withstanding extreme cold and saline marine conditions remains a significant unresolved challenge with broad implications for the maintenance and restoration of marine infrastructure. In this work, we developed a new class of functional materials, aluminosilicate-epoxy composites with self-initiated, frontal curing and seawater resistance, to address this challenge. A catalyzed stoichiometric frontal polymerization strategy was employed to overcome the fundamental chemical incompatibility between the frontal curing of epoxy and the alkali-activated geopolymerization of aluminosilicate. Distinct from traditional external photo- or thermal stimuli, calcium oxide hydration was used to trigger frontal curing in seawater, thereby eliminating external energy input during both initiation and curing. The underwater front-cured aluminosilicate-epoxy composite exhibits a compressive strength of 48.3 MPa and an adhesive strength of 5.57 MPa on steel within one hour. The key property indicator (KPI), defined as the ratio of minimal operational compressive strength to the required curing time, outperforms state-of-the-art performance by 87.4-fold. Moreover, the composites exhibit high ultraviolet resistance (92% strength retention) and seawater resistance (96.25% strength retention with 0.26% mass loss) after 720 hours of UV exposure and 7 days of seawater immersion. The frontal curing of seawater-resistant hybrid materials represents a paradigm shift in underwater repair, with substantial potential to transform marine infrastructure restoration.