Multilayer coating for flame retardant substrates

A method includes coating a substrate to provide a flame resistant substrate. In an embodiment, the method includes exposing the substrate to a cationic solution to produce a cationic layer deposited on the substrate. The cationic solution comprises cationic materials. The cationic materials comprise a polymer, a colloidal particle, a nanoparticle, a nitrogen-rich molecule, or any combinations thereof. The method further includes exposing the cationic layer to an anionic solution to produce an anionic layer deposited on the cationic layer to produce a layer comprising the anionic layer and the cationic layer. The anionic solution comprises a layerable material.U