Preparation and Properties of Transparent, Thermally Insulating, and Flexible SiO2 Aerogels

Highlights A transparent, flexible SiO 2 aerogel was prepared via ambient pressure drying using an optimized MTMS–DMDMS composite silicon source. The aerogel achieves a visible light transmittance of 89.74% and a low thermal conductivity of 0.027 W/(m·K). The introduction of DMDMS enhances flexibility, increasing compressive strength by 22.4% compared to pure MTMS aerogels. The material exhibits excellent hydrophobicity with a water contact angle of 125.98° and a low density of 0.1802 g/cm 3 . A multi-parameter cooperative regulation strategy enables balanced optimization of optical, thermal, and mechanical properties. The main findings. Using tetramethylammonium hydroxide (TMAOH) as the alkaline catalyst, a water/MTMS molar ratio of 7:1, and Pluronic F-127 (F127) as the surfactant yields a single-silicon-source SiO 2 aerogel with uniform pore structure, 93.50% porosity, 125.98° water contact angle, and 89.74% transmittance at 800 nm. Constructing an MTMS–DMDMS composite silicon source with a molar ratio of 9:1, 6 mL water addition, and 2.0 g F127 produces a flexible aerogel with 22.4% higher compressive strength, 70.15% visible transmittance, and thermal conductivity as low as 0.027 W/(m·K), achieving balanced mechanical, optical, and thermal insulation properties. The implications of the main findings. The optimized single-silicon-source preparation route enables stable, low-cost ambient pressure synthesis of transparent, hydrophobic SiO 2 aerogels, supporting scalable manufacturing for building energy-saving applications. The MTMS–DMDMS composite system resolves the trade-off between transparency, thermal insulation, and mechanical flexibility, providing a design paradigm for high-performance transparent thermal insulation materials used in glazing, smart facades, and optical insulation components. SiO 2 aerogels are promising candidates for energy-efficient glazing because of their low thermal conductivity and optical transparency; however, conventional formulations often fail to reconcile optical, thermal, and mechanical performance. This work aimed to resolve this bottleneck via controllable sol–gel synthesis and ambient pressure drying. Using methyltrimethoxysilane (MTMS) as the single silicon source, this study systematically explored the effects of alkaline catalyst type, water-to-MTMS ratio, and surfactant selection, and further developed an MTMS–dimethyl dimethoxy silicane (DMDMS) composite silicon source. Tetramethylammonium hydroxide (TMAOH) catalysis, a water-to-MTMS molar ratio of 7:1, and Pluronic F-127 (F127) surfactant yielded a uniform, hydrophobic aerogel with 93.50% porosity and 89.74% transmittance at 800 nm. The optimized composite system (MTMS:DMDMS = 9:1, 6 mL water, 2.0 g F127) enhanced compressive strength by 22.4% relative to pure MTMS aerogel, with 70.15% visible transmittance and thermal conductivity of 0.027 W/(m·K). These results demonstrate that multi-parameter formulation control can achieve a practical balance among mechanical robustness, optical transparency, and thermal insulation. This study provides a theoretical and process foundation for the engineering application of high-performance transparent thermal insulation materials.