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Molecular design of AEC tri-block anionic surfactant towards rational synthesis of targeted thick-walled mesoporous silica
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry. (Osamu Terasaki)
2009 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, Vol. 19, 3404-3411 p.Article in journal (Refereed) Published
Abstract [en]

Here we report a new synthesis strategy to synthesize thick-walled two dimensional hexagonal mesoporous silicas, using tri-block surfactant fatty alcohol ether carboxylate [AEC: CnH2n+1O(CH2CH2O)mCH2COONa] with two different hydrophilic head groups of (EO)x-block and anionic carboxylate. The unique formation of double-layer silica wall arose from two types of hydrophilic head groups via the silica source condensation led to an obvious increase in the wall thickness. The successful carbon replication proved the existence of micropores formed by imbedded (EO)x-block and electrostatic bonding of carboxylate head group and organic group of co-structuredirecting agent. The template-free mesoporous silica showed a high hydrothermal stability due to the thick wall.

Place, publisher, year, edition, pages
United Kingdom: The Royal Society of Chemistry , 2009. Vol. 19, 3404-3411 p.
Keyword [en]
mesoporous, wall thickness, molecular design, AEC surfactant
Research subject
Materials Science
URN: urn:nbn:se:su:diva-29616DOI: 10.1039/b822742jOAI: diva2:234479
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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Gao, Chuanbo
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