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Molecular design of the surfactant and the co-structure-directing agent (CSDA) toward rational synthesis of targeted anionic surfactant templatedmesoporous silica
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry. (Osamu Terasaki)
2007 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, Vol. 17, 3591-3602 p.Article in journal (Refereed) Published
Abstract [en]

The formation of anionic surfactant templated mesoporous silica (AMS) is investigated from the perspective of the geometrical molecular design of the surfactant and the co-structure-directing agent (CSDA) toward the rational synthesis of the targeted mesostructure. Increasing the geometrical size of two types of head group of the anionic surfactant in the order (i) sulfonate, sulfate and phosphate, and (ii) carboxylate, N-acylalanate/N-acylglycinate and N-acylglutamate, resulted in the mesophase changing from a disordered or lamellar phase to two-dimensional (2D) hexagonal (p6mm) and three-dimensional (3D) cage-type (hexagonal and a modulated cubic phase) with increasing order of the organic/inorganic interface curvature. A change in the chain length of the surfactant also led to different surfactant packing and mesophase interfacial curvatures, and resulted in a change in mesophase from a modulated cage-type mesophase to cubic Fd-3m, cubic Pm-3n and a disordered cage-type mesophase. The geometrical change in the CSDA resulted in an increasing micellar curvature in the order: aminopropyl , N-methylaminopropyl, N,N-dimethylaminopropyl trimethoxysilane, which led to a change of mesophase from bicontinuous cubic Pn-3m to 2D-hexagonal p6mm. An increase in the CSDA/surfactant ratio in the synthesis gave rise to the mesophase change from a disordered cage-type mesophase to cubic Fm-3m or from lamellar to 2D-hexagonal p6mm, and elemental analysis results showed that the mesoporous silicas have an increased loading of organic moieties using the CSDA method.

Place, publisher, year, edition, pages
United Kingdom: The Royal Society of Chemistry , 2007. Vol. 17, 3591-3602 p.
Keyword [en]
mesoporous silica, anionic surfactant, co-structure directing agent, mesophase control
Research subject
Materials Science
URN: urn:nbn:se:su:diva-29614DOI: 10.1039/b704398hISI: 000248917400016OAI: diva2:234473
Available from: 2009-09-09 Created: 2009-09-08 Last updated: 2009-09-09Bibliographically approved
In thesis
1. Formation mechanism of anionic-surfactant-templated mesoporous silica (AMS)
Open this publication in new window or tab >>Formation mechanism of anionic-surfactant-templated mesoporous silica (AMS)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This dissertation is focused on synthesis, characterization and formation mechanism of anionic-surfactant-templated mesoporous silica (AMS).

Structural control mechanisms of AMS are investigated. First, different ionization degree of anionic surfactant affected by the acidity or alkalinity of the synthesis system gives rise to different charging density of micelles and therefore determines the organic/inorganic interface curvature, producing mesophases from cage-type to cylindrical, bicontinuous and lamellar. Second, mesocage/mesocage electrostatic repulsive interaction affects the formation of cage-type mesostructure, which is derived from a full-scaled synthesis-field diagram of AMS. The mesocage/mesocage interaction changes with charge density of mesocages and gives rise to their different packing manners. Third, the structural properties of AMS materials could be tuned by molecular features of surfactant and co-structure-directing agent (CSDA).

The pore size of AMS is found to be controlled by alkyl chain length, ionization degree of surfactant and the CSDA/surfactant ratio. Alkyl chain length of surfactant determines size of micelles and thus mesopores. Larger ionization degrees of anionic surfactant give rise to smaller pore sizes due to thermodynamic coiling of alkyl chains of surfactant. The hydrophobic interactions between the pendant organic groups of CSDA on the silica wall and the hydrophobic core of the micelles drive a contraction of the mesopores.

A mesoporous silica with novel bicontinuous cubic Pn-3m structure has been prepared using a diprotic anionic surfactant. 3d-reconstruction of the structure shows that it is bicontinuous composed of an enantiomeric pair of 3d mesoporous networks that are interwoven with each other, divided by a D surface. Inverse replication suggests the possible presence of ordered complimentary micropores in the material.

Place, publisher, year, edition, pages
Stockholm: Department of Physical, Inorganic and Structural Chemistry, Stockholm University, 2009. 75 p.
mesoporous silica, anionic surfactant, formation mechanism, structural control
National Category
Other Basic Medicine
Research subject
Structural Chemistry
urn:nbn:se:su:diva-29628 (URN)978-91-7155-932-6 (ISBN)
Public defence
2009-10-06, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius vägen 16 B, Stockholm, 13:30 (English)
Available from: 2009-09-15 Created: 2009-09-08 Last updated: 2009-09-15Bibliographically approved

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