title: Clay exfoliation and polymer/clay aerogels by supercritical carbon dioxide.
abstract: Supercritical carbon dioxide (scCO2) treatments of a montmorillonite (MMT) intercalated with ammonium cations bearing two long hydrocarbon tails (organo-modified MMT, OMMT) led to OMMT exfoliation, with loss of the long-range order in the packing of the hydrocarbon tails and maintenance of the long-range order in the clay layers. The intercalated and the derived exfoliated OMMT have been deeply characterized, mainly by X-ray diffraction analyses. Monolithic composite aerogels, with large amounts of both intercalated and exfoliated OMMT and including the nanoporous-crystalline δ form of syndiotactic polystyrene (s-PS), have been prepared, by scCO2 extractions of s-PS-based gels. Also for high OMMT content, the gel and aerogel preparation procedures occur without re-aggregation of the exfoliated clay, which is instead observed for other kinds of polymer processing. Aerogels with the exfoliated OMMT have more even dispersion of the clay layers, higher elastic modulus and larger surface area than aerogels with the intercalated OMMT. Extremely light materials with relevant transport properties could be prepared. Moreover, s-PS-based aerogels with exfoliated OMMT could be helpful for the handling of exfoliated clay minerals.
authors.affiliation: Department of Chemistry and Biology and INSTM Research Units, Università degli Studi di Salerno Fisciano, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Longo
authors.affiliation: Department of Chemistry and Biology and INSTM Research Units, Università degli Studi di Salerno Fisciano, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Mauro
authors.affiliation: Department of Chemistry and Biology and INSTM Research Units, Università degli Studi di Salerno Fisciano, Italy.
authors.forename: Christophe
authors.initials: C
authors.lastname: Daniel
authors.affiliation: Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano Milano, Italy ; CNR, Istituto per lo Studio delle Macromolecole, National Research Council Milano, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Galimberti
authors.affiliation: Department of Chemistry and Biology and INSTM Research Units, Università degli Studi di Salerno Fisciano, Italy.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Guerra
keywords: cationic clays; monolithic aerogels; montmorillonite; nanoporous-crystalline δ form; organoclays; syndiotactic polystyrene