Aerogels containing silicon bonded polymers
a technology of aerogels and polymers, which is applied in the field of aerogels containing silicon bonded polymers, can solve the problems of inability to produce transparent aerogel composites, collapse of filigranes, and inability to use the mixture generally used to prepare xerogels to prepare aerogels, so as to improve various physical and mechanical properties
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example 1
[0067]This example illustrates the formation of a triethoxysilyl terminated polyether. 46.0 g of 3-isocyanatopropyltriethoxysilane was added to a mixture of 400 g of amine-terminated polyoxypropylene diols (Jeffamine®XTJ510, Mw=4000, commercially available from Hutsman corporation) and 400 ml of anhydrous THF, following by vigorous stirring at ambient temperature. The completion of this reaction can be monitored by IR spectroscopy. It was observed that the strong and narrow band at 2274 cm−1 assigned to the vibration of isocyanate group of the to 3-isocyanatopropyltriethoxysilane disappeared at the end of the reaction (approx 1 hour). Example 1 serves as an exemplar for the source of the linear polymer.
example 2
[0068]This example illustrates the formation of a triethoxysilyl terminated polyoxypropylene. 49.47 g of 3-isocyanatopropyltriethoxysilane (Aldrich) was added to a mixture of 200 g of amine-terminated polyoxypropylene diols (Jeffamine® D2000, Mw=2000, commercially available from Hutsman corporation) and 200 ml of anhydrous THF, following by vigorous stirring at ambient temperature. The completion of this reaction can be monitored by IR spectroscopy. It was observed that the strong and narrow band at 2274 cm−1 assigned to the vibration of isocyanate group of the to 3-isocyanatopropyltriethoxysilane disappeared at the end of the reaction (less than 0.5 hour). Example 2 serves as an exemplar for the source of the linear polymer.
example 3
[0069]This example illustrates the formation of a polyoxypropylene modified silica aerogel monolith with 5 wt % loadings of polyoxypropylene (Mw2000). 25 g of water were added to a mixture of 52.7 g tetramethylorthosilicate (TMOS), 1.7 g of the polymer from Example 2 and 350 ml of methanol, following by 1 hour mixing at ambient temperature. The combination was gelled by addition of 0.6 g formamide and 6.0 g ammonia methanol solution (15.4 wt % ammonia). The resultant gels were first aged in ammonia ethanol solution (4.85 wt %) at ambient temperature, followed by aging in hexamethyldisilazane (5% v / v) solution for 3 days at ambient temperature. The gels remained highly transparent after CO2 supercritical extraction. The average thermal conductivity of the resultant aerogel monoliths was 13.1 mW / m·K under ambient conditions, and the average density of these monoliths was 0.07 g / cm3.
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