Fabrication of phytic acid modified mesoporous silica and its synergistic flame retardancy with a DOPO derivative in polyacrylonitrile nanofibers

Polyacrylonitrile (PAN) nanofiber skeleton has become essential components in designing high-performance composite materials such as solid electrolytes, however, its widespread application is still limited by high flammability. In this work, a phytic acid (PA)-modified mesoporous silica (PA-mSiO ₂ ) was fabricated and then incorporated into PAN nanofibers together with a phenethyl-bridged DOPO derivative (DiDOPO) via electrospinning. The morphology and structure of the prepared PA-mSiO ₂ and the resulting composite nanofiber skeleton were characterized. The flame retardancy of the PAN composite nanofiber skeleton was evaluated, which revealing a pronounced synergistic effect between PA-mSiO ₂ and the DOPO derivative. The combined system was more effective than the individual additives in suppressing combustion, as evidenced by a significantly lower peak heat release rate (pHRR) and total heat release (THR), along with a higher limiting oxygen index (LOI) and char yield. The synergistic mechanism was investigated, indicating that PA-mSiO ₂ primarily acted in the condensed phase by catalyzing the formation of a stable, phosphorus-rich siliconaceous char layer that acted as a thermal barrier. Simultaneously, the DiDOPO derivative functioned in the gas phase by releasing flame-inhibiting radicals. This work demonstrates an effective strategy for creating flame-retardant PAN nanofiber skeleton with potential applications in lithium-ion batteries.