Layer-by-Layer Assembly of 2D Nanomaterials into Flame-Retardant Coatings for Fire-Safe Polymers

The use of surface treatments for conferring flame retardant behavior to flammable polymers (bulk materials, textiles, and foams) is now a well-established and effective strategy. Being able to place the flame retardant exclusively on the polymer surface, the critical interface between the condensed phase and the gas phase is important for quickly suppressing fire without altering bulk polymer behavior. The flame retardant is placed only where it is trulyneeded. Among the surface engineered approaches, layer-by-layer (LbL) assembly has attracted great interest from both the academic and industrial communities. This technique is very simple, shows a very low impact on the environment, and can be tailored to any polymer “object” (independent of its shape, size, and complexity). This review is focused on the state of the art in the use of the LbL method for the design of effective flame retardant coatings containing 2D nanostructures, highlighting the current limitations and providing some future perspectives.