Synergistic co-assembly of phytic acid and pluronic F127 for environmentally benign, mechanically robust, and fire-resistant silica xerogel monoliths

PA/F127 co-assembly forms robust Si–O–P bonds and uniform microstructure in silica xerogels. • Xerogels integrate high strength, monolithicity, self-extinguishing ability, and thermal insulation. • PA's dual role enables rapid gelation, bypassing conventional slow acid-catalyzed growth. • Excellent fire resistance with minimal flame damage outperforms commercial silica aerogel sheets. • A green, additive-free strategy overcomes the flame-retardancy vs. mechanical-integrity trade-off. Conventional flame-retardant additives often raise environmental and health concerns due to their toxicity and persistence. Developing high-performance, inherently fire-resistant silica xerogel monoliths via scalable ambient pressure drying remains a significant challenge, as mechanical robustness, monolithic integrity, and flame retardancy are typically mutually exclusive. This study addresses this issue by introducing a green and synergistic strategy using bio-derived phytic acid (PA) and the amphiphilic block copolymer Pluronic F127 to direct the sol-gel co-assembly of a methyltrimethoxysilane/tetraethoxysilane (MTMS/TEOS) system. PA serves dual roles: as a potent biobased acid catalyst, it accelerates precursor hydrolysis, and as a non-toxic, multidentate cross-linker, it forms persistent Si–O–P bonds that chemically reinforce the silica network. F127 acts as a microstructure director, templating a homogeneous gel network with robust inter-particle connectivity. This cooperative action enables rapid gelation (within 1–20 min) and yields monolithic phosphorus-incorporated silica (P-silica) xerogels. The optimized material exhibits excellent mechanical performance (compression strength = 0.140 MPa, strain = 60.3%), outstanding thermal stability (90.3 wt% residual mass at 1000 °C), and superior fire resistance, showing immediate self-extinguishment and minimal damage upon direct flame impingement. It also provides effective thermal insulation, surpassing commercial silica aerogel sheets at a thickness of 3 mm. By replacing conventional hazardous flame retardants with benign, biobased PA and achieving a unique property synergy, this work presents a viable and environmentally sound design principle for advanced thermal insulation materials in fire-risk environments, contributing to safer and more sustainable material solutions. Download: Download high-res image (123KB) Download: Download full-size image