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, phytic acid-modified mesoporous silica (PA-mSiO 2 ) was prepared via the sol-gel method followed by surface modification, and then it was incorporated together with a phenethyl-bridged DOPO derivative (DiDOPO) into a PAN precursor solution to fabricate composite nanofibers 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 reductions in the peak heat release rate (pHRR) and total heat release (THR) by 34.5% and 12.7% respectively, along with increases in the limiting oxygen index (LOI) and char yield by 52.5% and 18.1% respectively. 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, which may hold potential for application in high-safety electrolyte design.