Thermal degradation behavior of polystyrene/magadiite nanocomposites prepared by surface-initiated nitroxide-mediated radical polymerization

Exfoliated polystyrene (PS)/magadiite nanocomposites with a high suppression effect on thermal degradation were successfully prepared by in situ nitroxide-mediated radical polymerization of styrene monomer from the magadiite interlayer surface. Surface-initiated polymerization of styrene was conducted from the radical initiators immobilized on magadiite at 398 K. The number-average molecular weight (M_n) of the grafting PS increased with monomer conversion keeping a relatively low polydispersity index. The initiator efficiency was estimated to be less than 10% by size exclusion chromatography analysis. The results of X-ray diffraction and transmission electron microscopy suggested that the nanocomposites provided exfoliated structures. The fine dispersion state of magadiite in PS matrices contributed to effective suppression of the thermal degradation of PS. In addition, an interesting difference in the shape of the final residues was observed. Thermal decomposition of exfoliated PS/magadiite nanocomposites gave a substantial rigid solid as a residue, the shape of which largely depended on the concentrations of magadiite in the PS matrices. For instance, the thermal decomposition of nanocomposites produced a seamless residue that can effectively retard the decomposition rate. In contrast, the simple mixture of PS and magadiite was thermally decomposed to be powdery ash in the final residues.