Tuning the Mesostructures of Vinyl Silica by Adjusting the Micellar Curvature

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• 作者：Yanqin Wang ; Yaojun Wang ; Chia-Min Yang ; Guanzhong Lu ; and Ferdi Sch&uuml ; th
• 刊名：Langmuir
• 出版年：2006
• 出版时间：June 6, 2006
• 年：2006
• 卷：22
• 期：12
• 页码：5491 - 5496
• 全文大小：318K
• 年卷期：v.22,no.12(June 6, 2006)
• ISSN：1520-5827

文摘

In our previous study (Wang, Y. Q.; Yang, C.-M.; Zibrowius, B.; Spliethoff, B.; Lindén, M.; Schüth, F. Chem.Mater. 2003, 15, 5029), mesoporous vinyl-functionalized silica (vinyl silica) with hexagonal P6mm and cubic Ia3dstructures has been synthesized at different loadings of vinyl groups and at different concentrations of sodium chloridewhen triblock copolymer P123 was used as a template. Our further investigations presented in this article reveal thatat a loading of 10% vinyl groups, well-ordered cubic Ia3d structure was obtained at a low concentration of Na₂SO₄(0.5 M) and the hexagonal structure was produced at 1.0 M NaCl. When NaNO₃ was used as the inorganic salt, thehexagonal structure was still maintained even at a salt concentration of 2.0 M. The result is in accordance with theHofmeister series order (salting-out effect): SO₄^2- > Cl^- > NO₃^-. The lowering of the acidity also induced theformation of the cubic Ia3d structure. At 20% loading, hexagonal structure can be obtained by adding the morehydrophilic Pluronic F127 (EO₁₀₆PO₇₀EO₁₀₆) to the acidic solutions of P123, but the hexagonal structure cannot beproduced with pure P123 under the synthesis conditions investigated. All of these results can be rationalized throughhydrophilic-hydrophobic balance and the change in micellar curvature. Furthermore, 10% mercaptopropyl-functionalizedmesoporous silica with cubic Ia3d structure was designed and synthesized successfully with the assistance of aninorganic salt (NaCl) in an acidic solution of P123, which is the first example of mercaptopropyl-functionalizedlarge-pore mesoporous silica with high loadings.