Critical Micelle Concentrations of Cetyltrimethylammonium
Chloride and Their Influence on the Periodic Structure
of Mesoporous Silica¹

Daqing Li^a, Hao Li^a, Yan Fu^b, Jin-Li Zhang^b, Wei Li^b*, Yong-Cai Han^b, and Li Wang^b

^a Qilu Hospital of Shandong University, Jinan 250012, P.R. China

^b School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P.R. China

*e-mail: liwei@tju.edu.cn

Received December 12, 2007

Abstract—The influence of micelle morphology transformation on the structure of mesoporous materials is
fundamental in designing optimal, well-ordered, mesoporous materials. Firstly, the steady-state fluorescence
technique was adopted to determine the first and second critical micelle concentrations of cetyltrimethylammo-
nium chloride (CTAC) as 125 and 210 mmol L¹ in an equimolar mixture of water and ethanol at 25C. Using
tetraethylorthosilicate (TEOS) as the precursor, mesoporous silicas (with a surface area of 545.7–1210.5 m
545.7 ~ 1210.5 m² g¹ and a pore volume of 0.26 ~ 0.80 cm³ g¹) were synthesized with the CTAC templates
in the equimolar mixture of water and ethanol. Characterization by small-angle X-ray diffraction and N₂
adsorption/desorption techniques revealed that the surface area and pore volume of silica increased with the
content of CTAC, whereas there existed a transition point at the CTAC/TEOS ratio of 0.15 corresponding to the
fade-away of well-ordered mesoporous structure. The negative effect of the much higher content CTAC on the
periodic structure of mesoporous silica is attributed to micelle transformation from spheres to cylinders related
to the second critical micelle concentration of CTAC.

DOI: 10.1134/S1061933X08060100

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