Polymer aerogels have become a major research focus in the field of aerogels. With unique advantages over inorganic aerogels including higher strengths and compressive moduli, greater toughness and the ability to be fabricated as a flexible thin film; polymer aerogels have supplanted inorganic aerogels in numerous applications. Of the many polymer aerogels presently available, polyimide aerogels have a distinction for possessing high thermal stability as well as excellent mechanical properties. Research on this class of polymer aerogels has shown that while the onset of thermal decomposition for these materials is typically very high (greater than 500 °C), the aerogels will undergo dramatic thermally induced shrinkage at temperatures below their glass transition temperature (T<sub>g</sub>) or their decomposition temperature. Attempts to minimize thermal shrinkage were successful when a bulky, space-filling moiety was incorporated into the polymer backbone. An array of 20 polyimide aerogels were synthesized from 3,3’4,4’-biphenyltetracarboxylic dianhydride (BPDA) and 4,4’-oxydianiline (ODA) and in some cases BPDA and a combination of ODA and 9,9’-bis(4-aminophenyl)fluorene (BAPF). The aerogels were cross-linked with 1,3,5-benzenetricarbonyl trichloride (BTC). The polymer concentration, n-value and molar concentration of ODA and BAPF were varied. The resultant aerogels were subjected to isothermal aging at 150 °C and 200 °C for up to 500 hours. Samples containing BAPF showed a reduction in thermally induced shrinkage by as much as 50% compared to unmodified polyimide aerogels.

Synthesis and characterization of cardo-diamine containing polyimide aerogels

251st National Meeting (2016)

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