Tuning the Mesostructures of Vinyl Silica by Adjusting the Micellar Curvature

Abstract

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 Ia3d structures has been synthesized at different loadings of vinyl groups and at different concentrations of sodium chloride when triblock copolymer P123 was used as a template. Our further investigations presented in this article reveal that at 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, the hexagonal structure was still maintained even at a salt concentration of 2.0 M. The result is in accordance with the Hofmeister series order (salting-out effect): SO4(2-) > Cl- > NO3(-). The lowering of the acidity also induced the formation of the cubic Ia3d structure. At 20% loading, hexagonal structure can be obtained by adding the more hydrophilic Pluronic F127 (EO106PO70EO106) to the acidic solutions of P123, but the hexagonal structure cannot be produced with pure P123 under the synthesis conditions investigated. All of these results can be rationalized through hydrophilic-hydrophobic balance and the change in micellar curvature. Furthermore, 10% mercaptopropyl-functionalized mesoporous silica with cubic Ia3d structure was designed and synthesized successfully with the assistance of an inorganic salt (NaCl) in an acidic solution of P123, which is the first example of mercaptopropyl-functionalized large-pore mesoporous silica with high loadings.

Organically Functionalized Mesoporous Silica by Co‐structure‐Directing Route

“…As is widely recognized, the salting-in and saltingout properties of a counterion following the Hofmeister series play an important role in this process. [67][68][69][70][71] Carboxylate is a salting-out anion (relative to Cl − ) and is well hydrated. Counterions that have an intense electrostatic fi eld interact strongly with the carboxylate surfactant, thereby weakening the repulsions between the headgroups of the surfactant and inducing a decrease in the organic/inorganic interface curvature.…”

Coordination environment friendly silicon in copper(I) chloride π-complexes with tetravinylsilane and dimethyltetravinyldisiloxane

“…Furthermore, Cu(I)-olefin adducts are well known as sensitive coatings (elements, materials) of piezoelectric sensors [8]. It is noteworthy that there was a rash of reports about possibility of silica gel modification with unsaturated compounds [9][10][11] and further metal ions complexation [12].…”

Hierarchically structured biphenylene-bridged periodic mesoporous organosilica

“…The presence of Li + ions and Cl À ions can change the micellar hydration behavior of the pluronic F127 solution and thus change the curvature of the micelles. 55,56,58,59 Specifically, on the one hand, the Cl À ion has the effect of dehydrating hydrophilic groups of F127 micelles and thus decreasing the curvature of F127 micelles. On the other hand, hydrated Li + ions can form complexes with the PEO chains in the micellar corona region, [58][59][60] which can enlarge the hydrophilic head groups of the F127 micelles.…”

“…55,56,58,59 Specifically, on the one hand, the Cl À ion has the effect of dehydrating hydrophilic groups of F127 micelles and thus decreasing the curvature of F127 micelles. On the other hand, hydrated Li + ions can form complexes with the PEO chains in the micellar corona region, [58][59][60] which can enlarge the hydrophilic head groups of the F127 micelles. In general, the effect of hydrated Li + is stronger than that of Cl À , such that the size of the hydrophilic head groups of F127 micelles can be increased, which can lead to more hydrophilic F127 micelles with higher curvature.…”