Design and Synthesis of a Bio-Based DOPO-ITA Flame-Retardant Monomer for Modifying CO2-Based Polycarbonates

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. Graphical Schematic illustration of the synthesis, thermal stability, and their flame retardant mechanism of PPCD.