Design and Synthesis of a Bio‐Based <scp>DOPO</scp> ‐ <scp>ITA</scp> Flame‐Retardant Monomer for Modifying <scp> CO ₂ </scp> ‐Based Polycarbonates

ABSTRACT This study tackles the poor flame retardancy of CO 2 ‐based poly(propylene carbonate) (PPC) by synthesizing a known biobased phosphorus‐containing monomer, DOPO‐ITA, and for the first time, incorporating it as a flame‐retardant functional third monomer into the copolymerization of CO 2 and propylene oxide, yielding flame‐retardant PPCD. Structural characterization confirmed the successful synthesis. PPCD exhibited outstanding flame retardancy, with a limiting oxygen index of 32.2%, a V‐0 rating, and no melt dripping. SEM analysis provided insights into the flame‐retardant mechanism. Thermal analysis showed a 51% increase in initial decomposition temperature and a 36% rise in glass transition temperature, indicating significantly improved thermal stability. Mechanically, tensile strength and Young's modulus increased by 143% and 420%, respectively. This work presents an efficient, eco‐friendly strategy for enhancing the flame retardancy of CO 2 ‐based polycarbonates and highlights the promise of biobased phosphorus‐containing flame retardants in sustainable materials.