Molecular dynamics insights into Ti3C2 MXene/chitosan composite as a flame-retardant barrier

Abstract Two-dimensional Ti 3 C 2 MXenes exhibit remarkable thermal stability and flame resistance, while hybridisation with bio-based chitosan (CS) enhances their effectiveness as flame-proof coating. However, the underlying flame-retardant (FR) mechanisms remain insufficiently resolved at the atomistic scale. Herein, reactive molecular dynamics simulations (MD-ReaxFF) alongside experiments (TGA-FTIR, SEM, XRD, XPS) elucidate the FR pathways of MXene/CS nanosheets. MXene/CS exhibits flame retardancy through three synergistic pathways: (1) releasing organic volatiles to dilute oxidisers; (2) depositing hydroxyl and nitrogen groups to passivate reactive sites; and (3) reinforcing char formation by strengthening C-C and Ti-C bonding. Multilayer MXene/CS coatings exhibit sequential FR behaviour, where sacrificial TiO 2 layers, interlayer carbonisation, and volatile exclusion collectively maintain structural stability under extreme heating. Experimental validation confirms the organic volatiles, enhanced char yield, TiO 2 transformation, and surface functionalisation. These insights establish a mechanistic framework for MXene-based hybrids and highlight CS as a sustainable charring agent, offering design principles for future lightweight and multifunctional flame-retardant coatings.