Multifunctional Porous Aramids (aerogels) by Efficient Reaction of Carboxylic Acids and Isocyanates
Polymerization of trifunctional polyaromatic carboxylic acids and isocyanates in dilute DMF solutions using the rather underutilized reaction of the carboxylic acid group (-COOH) with isocyanates (-NCO) towards amides (-NH(CO)-) induces early phase separation of surface-active aramid nanoparticles that form a solvent-filled 3D network stabilized against collapse by the chemical energy of the interparticle covalent bridges (crosslinks). Those wet-gels can be dried with liquid CO2 taken out at the end as a supercritical fluid into lightweight (bulk density ∼0.3 g cm-3) highly porous (77% v/v) multifunctional materials classified as aerogels with high specific energy absorption (37 J g-1), open-air speed of sound (338 m s-1) and Styrofoam-like thermal conductivity (0.028 W m -1 K-1). © The Royal Society of Chemistry 2011.
N. Leventis et al., "Multifunctional Porous Aramids (aerogels) by Efficient Reaction of Carboxylic Acids and Isocyanates," Journal of Materials Chemistry, Royal Society of Chemistry, Jan 2011.
The definitive version is available at http://dx.doi.org/10.1039/c1jm11472g
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