Title: Molecular Simulations of the Synthesis of Periodic Mesoporous Silica Phases at High Surfactant Concentrations

Abstract

Molecular dynamics simulations of a coarse-grained model are used to study the formation mechanism of periodic mesoporous silica over a wide range of cationic surfactant concentrations. This follows up on an earlier study of systems with low surfactant concentrations. We started by studying the phase diagram of the surfactant-water system and found that our model shows good qualitative agreement with experiments with respect to the surfactant concentrations where various phases appear. We then considered the impact of silicate species upon the morphologies formed. We have found that even in concentrated surfactant systems ← in the concentration range where pure surfactant solutions yield a liquid crystal phase ← the liquid-crystal templating mechanism is not viable because the preformed liquid crystal collapses as silica monomers are added into the solution. Upon the addition of silica dimers, a new phaseseparated hexagonal array is formed. The preformed liquid crystals were found to be unstable in the presence of monomeric silicates. In addition, the silica dimer is found to be essential for mesoscale ordering at both low and high surfactant concentrations. Our results support the view that a cooperative interaction of anionic silica oligomers and cationic surfactants determines the mesostructure formation in the M41S familymore » of materials.« less

Authors:

Chien, Szu-Chia ;

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• Search DOE PAGES for ORCID "0000-0002-1239-7258"

Pérez-Sánchez, Germán ^[1]; Gomes, José R. B.  ^[2];

• Search DOE PAGES for author "Gomes, José R. B."
• Search DOE PAGES for ORCID "0000-0001-5993-1385"

Cordeiro, M. Natália D. S. ^[3]; Jorge, Miguel  ^[4];

• Search DOE PAGES for author "Jorge, Miguel"
• Search DOE PAGES for ORCID "0000-0003-3009-4725"

Auerbach, Scott M.; Monson, Peter A.

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1. CICECO-Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal, LAQV@REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua Campo Alegre 687, 4169-007 Porto, Portugal
2. CICECO-Aveiro Institute of Materials, Department of Chemistry, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
3. LAQV@REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua Campo Alegre 687, 4169-007 Porto, Portugal
4. Department of Chemical and Process Engineering, University of Strathclyde, 75 Montrose Street, Glasgow G1 1XJ, United Kingdom

Publication Date:

Fri Feb 17 00:00:00 EST 2017

Research Org.:

Univ. of Massachusetts, Amherst, MA (United States); University of Strathclyde

Sponsoring Org.:

USDOE

OSTI Identifier:

1352290

Alternate Identifier(s):

OSTI ID: 1423812; OSTI ID: 1423813; OSTI ID: 1507992

Grant/Contract Number:  

FG02-07ER46466

Resource Type:

Published Article

Journal Name:

Journal of Physical Chemistry. C

Additional Journal Information:

Journal Name: Journal of Physical Chemistry. C Journal Volume: 121 Journal Issue: 8; Journal ID: ISSN 1932-7447

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY