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

• Type: Article in International Scientific Journal
• Date: 2017

Authors

Chien, SC (Author) Other; Perez Sanchez, G (Author) Other; Gomes, JRB (Author) Other; Natalia N D S Cordeiro (Author) FCUP; Jorge, M (Author) Other; Auerbach, SM (Author) Other; Monson, PA (Author) Other

Journal

Title: Journal of Physical Chemistry C

Vol. 121

Pages: 4564-4575

ISSN: 1932-7447

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 25 Citations

Scopus - 26 Citations

Other information

Authenticus ID: P-00M-J9H

DOI: 10.1021/acs.jpcc.6b09429

Abstract (EN): 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 phase separated 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 family of materials.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 12