Post-Polymerization Modification of Polystyrene through\nMn-Catalyzed Phosphorylation of Aromatic C(sp<sup>2</sup>)–H\nBonds

The\nhigh flammability and lack of charrability of polystyrene (PS)\npose significant limitations on its broader applications. Therefore,\nthere is an urgent need for a straightforward and efficient method\nfor the synthesis of flame-retardant PS, which still poses a considerable\nchallenge. In this study, we present an efficient approach to enhance\nthe flame-retardant properties of PS through direct phosphorylation\nof aromatic C(sp<sup>2</sup>)–H bonds using commercially available\nand inexpensive manganese catalyst. A range of phosphonates served\nas reactive substrates to enable a tunable degree of polymer functionalization.\nThe corresponding phosphorylated PS specimens were determined by means\nof <sup>1</sup>H NMR, <sup>31</sup>P NMR, FTIR spectroscopy, and size\nexclusion chromatography. Microscale combustion calorimetry tests\nindicate that this protocol indeed enhances the flame-retardant performance\nof PS. Moreover, other advantages associated with the incorporation\nof the phosphonate group have been observed, including maintained\nthermal resistance and improved wettability. This cost-effective strategy\nof Mn-catalyzed C–H can also be utilized to directly obtain\nphosphonate modification of waste foamed PS and styrene acrylonitrile\ncopolymer, providing a method for the purpose of recycling and upgrading\nPS plastics.