Novel chiral-driven stereoisomerism dimension of fire safety and crystallization mechanisms in poly(lactic acid)

Although fire is the foundation of human civilization, the microscopic combustion reaction remains poorly defined, especially with respect to the influence of molecular chirality. Herein, stereochemistry is shown to modulate combustion pathways in polymers. When right-handed (R(-)) and left-handed (L(+)) chiral additives are introduced into bio-based poly(lactic acid) (PLA), enantiomeric matching between the additive and the polymer backbone governs both combustion kinetics and crystallization pathways. Remarkably, poly(D-lactic acid) (PDLA) exhibits superior flame resistance with the L(+) isomer, whereas poly(L-lactic acid) (PLLA) shows the opposite trend, favouring the R(-) isomer. In PMLA (1 : 1 mass mixture of PLLA and PDLA), the L(+) configuration most effectively suppresses combustion catalysis. Despite identical molecular compositions, the enantiomers induce divergent crystallization kinetics, generate stereochemical distinct carbonaceous residues, and promote differentiated gas-phase degradation channels during combustion. These results establish chirality as a previously unrecognized parameter for catalytic regulation of polymer pyrolysis and combustion, providing a molecular framework for stereochemical control of combustion behavior.