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Acidity of Alginate Aerogels Studied by FTIR Spectroscopy of Probe Molecules
Author(s) -
Valentin Romain,
Horga Raluca,
Bonelli Barbara,
Garrone Edoardo,
Di Renzo Francesco,
Quignard Françoise
Publication year - 2005
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200551144
Subject(s) - fourier transform infrared spectroscopy , ionotropic effect , supercritical drying , lewis acids and bases , chemistry , adsorption , supercritical fluid , aerogel , divalent , chemical engineering , brønsted–lowry acid–base theory , inorganic chemistry , materials science , catalysis , organic chemistry , nanotechnology , biochemistry , nmda receptor , receptor , engineering
Supercritical drying of alginate gels is an efficient way to prepare aerogels with high surface area (>300 m 2 · g −1 ). FTIR spectroscopy allows to monitor the adsorption of NH 3 from the gas phase onto the acid sites of the alginate. Free carboxylic groups are effective Brønsted sites, whereas the divalent cations used in the ionotropic gelation present the properties of Lewis sites. The ratio between Brønsted and Lewis sites provides infomation on the role of pH in alginate gelation and suggests that non‐buffered gelation by transition‐metal cations is a mixed ionotropic‐acid process.