Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/59751
Type: Artigo de periódico
Title: Physical chemistry of nanostructured molecular sieves by the study of phase diagrams: the case of the cetyltrimethylammonium bromide-tetramethylammonium silicate-water system
Author: Albuquerque, A
Vautier-Giongo, C
Pastore, HO
Abstract: A phase diagram for the system cetyltrimethylammonium bromide (CTAB)/tetramethylammonium silicate (TMASi)/water has been constructed in order to better understand the interactions between these precursors of the MCM-41 mesoporous molecular sieves. Three different CTAB concentration regions were analyzed: the dilute and semidilute regions, where simple surfactant species, such as monomers and spherical and nonspherical CTAB micelles, are found, and the concentrated region, involving liquid-crystalline phases. In the dilute and semidilute regions, the formation of a white nanostructured solid, having a hexagonal array similar to that found in MCM-41 materials, was observed. Precipitation of this solid requires some degree of surfactant monomer aggregation, which is favored by the presence of silicate anions. If micelles have already been formed, the material can be obtained at any CTAB concentration above a threshold concentration of silicate anions. These facts suggest that silicate anions have an important role in changing the aggregation and/or the shape of the surfactant aggregates. In the concentrated region, precipitation of the solid was not observed, but the presence of the silicate anions alter the characteristics of the liquid-crystalline phase formed by the surfactant. The system shows very complex and rich behavior and its investigation may be very useful in understanding the processes of nanostructured solid formation. (c) 2004 Elsevier Inc. All rights reserved.
Subject: nanostructured molecular sieves
phase diagram
cetyltrimethylammonium bromide
MCM-41
liquid crystals
Country: EUA
Editor: Academic Press Inc Elsevier Science
Rights: fechado
Identifier DOI: 10.1016/j.jcis.2004.10.065
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

Files in This Item:
File Description SizeFormat 
WOS000228025400041.pdf252.05 kBAdobe PDFView/Open


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.