▎ 摘　　要

Developing polymer nanocomposites with high thermal stability and excellent flame retardant performances at low loadings still remains a great challenge. Here, we constructed multilayered polystyrene (PS) nanocomposites consisting of graphitic carbon nitride nanosheets (g-C3N4 NSs) and reduced graphene oxide (RGO) using the layer by layer assembly technique. Microstructure analysis demonstrated the successfully alternative assembly of g-C3N4 NSs and RGO onto PS spheres through electrostatic interaction. The ternary PS nanocomposites showed the highest thermal stability. For instance, the temperature at maximum decomposition rate and the residual yield were increased by 15 degrees C and 5.89 wt%, respectively for PS nanocomposite with one number of g-C3N4/RGO bilayers (PS/CG1). Furthermore, the PS/CG1 exhibited dramatically lowest release of total pyrolysis gaseous products and the peak of heat release rate, indicative of the highest fire safety. Fire safety enhancement was attributed to the formation of compact network barriers that retarded the heat and mass transfer between combustion zone and underlying PS matrix.