Polyurethane Aerogels based on Cyclodextrins: High-Capacity Desiccants Regenerated at Room Temperature by Reducing the Relative Humidity of the Environment
Polyurethane aerogels were prepared from a rigid aromatic triisocyanate (tris(4-isocyanatophenyl)methane) and cage-shaped α-and ß-cyclodextrins as rigid polyols. Gelation was carried out in DMF using dibutyltin dilaurate as catalyst. Wet-gels were dried to aerogels (abbreviated as α-or ß-CDPU-xx) with supercritical fluid CO2. "xx" stands for the percent weight of the two monomers in the sol and was varied at two levels for each cyclodextrin: 2.5% and 15%. All aerogels were characterized with solid-state 113C and 15N NMR, CHN analysis, FTIR, XPS, SEM, and gas (N2 and CO2) sorption porosimetry. α-and ß-CDPU-xx aerogels were investigated as desiccants at room temperature. All materials had relatively higher capacities for water adsorption from high-humidity environments (99%) than typical commercial desiccants like silica or Drierite. However, α-CDPU-2.5 aerogels did stand out with a water uptake capacity reaching 1 g of H2O per gram of material. Most importantly though, adsorbed water could be released quantitatively without heating, by just reducing the relative humidity of the environment to 10%. All α-and ß-CDPU-xx aerogel samples were cycled between humid and dry environments 10 times. Their unusual behavior was traced to filling smaller mesopores with water and was attributed to a delicate balance of enthalpic (H-bonding) and entropic factors, whereas the latter are a function of pore sizes.
P. M. Rewatkar et al., "Polyurethane Aerogels based on Cyclodextrins: High-Capacity Desiccants Regenerated at Room Temperature by Reducing the Relative Humidity of the Environment," ACS Applied Materials and Interfaces, vol. 11, no. 37, pp. 34292-34304, American Chemical Society (ACS), Sep 2019.
The definitive version is available at https://doi.org/10.1021/acsami.9b10755
Keywords and Phrases
Aerogels; Cyclodextrin; Desiccant; Polyurethane; Regenerated; Relative Humidity; Reused; Water Adsorption
International Standard Serial Number (ISSN)
Article - Journal
© 2019 American Chemical Society (ACS), All rights reserved.
01 Sep 2019