Nuclear Magnetic Resonance Studies of Resorcinol-Formaldehyde Aerogels

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DOIResolve DOI: http://doi.org/10.1021/jp050610rS1089-5647(05)00610-3
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TypeArticle
Journal titleThe Journal Of Physical Chemistry B: Condensed Phase
ISSN15206106
Volume109
Issue22
Pages1121511222; # of pages: 8
AbstractIn this article, we report a detailed study of resorcinol-formaldehyde (RF) aerogels prepared under different processing conditions, [resorcinol]/[catalyst] (R/C) ratios in the starting sol-gel solutions, using continuous flow hyperpolarized 129Xe NMR in combination with solid-state 13C and two-dimensional wide-line separation (2D-WISE) NMR techniques. The degree of polymerization and the mobility of the cross-linking functional groups in RF aerogels are examined and correlated with the R/C ratios. The origin of different adsorption regions is evaluated using both coadsorption of chloroform and 2D EXSY 129Xe NMR. A hierarchical set of Xe exchange processes in RF aerogels is found using 2D EXSY 129Xe NMR. The exchange of Xe gas follows the sequence (from fastest to slowest): mesopores with free gas, gas in meso- and micropores, free gas with micropores, and, finally, among micropore sites. The volume-to-surface-area (Vg/S) ratios for aerogels are measured for the first time without the use of geometric models. The Vg/S parameter, which is related both to the geometry and the interconnectivity of the pore space, has been found to correlate strongly with the R/C ratio and exhibits an unusually large span: an increase in the R/C ratio from 50 to 500 results in about a 5-fold rise in Vg/S.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences
Peer reviewedYes
Identifier18077705
NPARC number12327371
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Record identifier6a109c26-5bd1-4b43-aaf8-f1429511ade2
Record created2009-09-10
Record modified2017-03-23
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