Water-retaining, tough and self-healing hydrogels and their uses as fire-resistant materials1

Hydrogels as fire-resistant materials have attracted great attention due to their high water content and tailored shapes that can cover various surfaces. As fire-resistant materials, hydrogels should be mechanically tough, self-healable, and able to retain water under ambient environment for a long period. However, this combination is rarely realized. Here in this work, a series of Li-alginate/poly(acrylamide-co-stearyl methacrylate) [Li-alginate/P(AAm-co-SMA)] hydrogels with fully physically cross-linked interpenetrating networks have been prepared. The obtained hydrogels exhibit the maximum fracture energy of ∼6800 J m⁻², which is high enough for being used as fire-resistant materials. A fire resistance test suggests that the hydrogel is capable of withstanding 1300 °C flame for 50 s. The self-healing property ensures the recovery of the fire-resistance properties of the gels after being scratched or damaged. The water retention capacity promises the time-effectiveness of fire-resistance lasting for 6 months and even longer. In a word, the Li-alginate/P(AAm-co-SMA) hydrogels are potentially being applied as fire-resistant coatings for structures, trees and fireproof clothes.