Refine
Document Type
- Article (2)
Language
- English (2)
Has Fulltext
- yes (2)
Is part of the Bibliography
- no (2)
Keywords
Institute
Reproducible Superinsulation Materials: Organosilica-Based Hybrid Aerogels with Flexibility Control
(2024)
In this study, we report highly crosslinked hybrid aerogels with an organic backbone based on vinylmethyldimethoxysilane (VMDMS) with tuneable properties. For an improved and highly reproducible synthesis, a prepolymer based on 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (D4V4) and VMDMS as monomers was prepared and purified. Di-tert-butylperoxide (DTBP) concentrations of 1 mol% initiate the radical polymerization of the mentioned monomers to achieve high yields of polymers. After purification, the obtained viscous polyorganosilane precursor could be reproducibly crosslinked with dimethyldimethoxysilane (DMDMS) or methyltrimethoxysilane (MTMS) to form gels in benzylic alcohol (BzOH), water (H2O) and tetramethylammonium hydroxide (TMAOH). Whereas freeze-drying these silica-based hybrid aerogels led to high thermal conductivity (>20 mW m−1K−1) and very fragile materials, useful aerogels were obtained via solvent exchange and supercritical drying with CO2. The DMDMS-based aerogels exhibit enhanced compressibility (31% at 7 kPa) and low thermal conductivity (16.5 mW m−1K−1) with densities around (0.111 g cm−3). The use of MTMS results in aerogels with lower compressibility (21% at 7 kPa) and higher density (0.124 g cm−3) but excellent insulating properties (14.8 mW m−1K−1).
The tedious and time-consuming solvent exchange during aerogel production was sped up using a standard Soxhlet extractor. Optimizing the setup with a vent and molecular sieve allowed to save up to 80% of the production time compared to batchwise extractions while maintaining state-of-the-art samples of silica and polyurethane aerogels, i.e. MTMS aerogels with a thermal conductivity of 15 mW m−1 K−1 and PU aerogels with 17 mW m−1 K−1 and good mechanical properties even after freeze-drying, which is generally more stressful than supercritical drying. The syntheses had to be carried out in high-boiling solvents, but adaptation and optimisation were made possible rapidly due to the method developed.
