Title

Polyurethane Aerogels based on Cyclodextrins: High-Capacity Desiccants Regenerated at Room Temperature by Reducing the Relative Humidity of the Environment

Abstract

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.

Department(s)

Chemistry

Comments

The Authors thank the Army Research Office under Award No. W911NF-14-1-0369 for financial support. We also thank Covestro LLC for the generous supply of Desmodur RE (TIPM) and the Materials Research Center of the Missouri University of Science and Technology for support with materials characterization.

Keywords and Phrases

Aerogels; Cyclodextrin; Desiccant; Polyurethane; Regenerated; Relative Humidity; Reused; Water Adsorption

International Standard Serial Number (ISSN)

1944-8244; 1944-8252

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2019 American Chemical Society (ACS), All rights reserved.

Publication Date

01 Sep 2019

PubMed ID

31490651

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