Multi-crosslinked gelatin-based composite hydrogel featuring high thermoelectric performance and excellent flame retardancy for intelligent fire-warning system.

The frequency occurrence of building fires necessitates response materials with high flame retardancy and temperature sensitivity. Herein, we synthesized a gelatin/poly(acrylamide-co-acrylic acid)/lithium bromide/sodium phytate/glycerol hydrogel (Gly-GAPL) using in situ radical polymerization and solvent exchange techniques. Gly-GAPL exhibits notable thermoelectric performance (the Seebeck coefficient: 8.66 mV/K), temperature sensitivity, commendable mechanical properties and flame retardancy. Remarkably, Gly-GAPL features a rapid response time, triggering an alarm within 2 s upon exposure to flame. Gly-GAPL is highly resistant to ignition and significantly enhances the fire resistance of wood coated with it. Furthermore, its high transparency, impressive water retention and adhesion further underscore its potential as a flame-retardant coating for various inflammable materials. Given its outstanding thermoelectric performance and temperature sensitivity, an early fire-warning system is rapidly activated, promptly sending alerts to smart devices. This work introduces a novel strategy for developing smart flame retardancy materials and advances the applications of ionic hydrogels in early fire-warning systems.