Control of Silica−Alkyltrimethylammonium Bromide Mesophases with 1,3,5-Trialkylbenzenes under Acidic Conditions

Abstract

This article reports the structural variation of SBA-type mesostructured silica formed from a mixture of tetraethyl orthosilicate (TEOS), alkyltrimethylammonium bromides, and 1,3,5-trialkylbenzenes under acidic conditions. Swollen 2D hexagonal mesophases were formed from the silica source and hexadecyltrimethylammonium bromide (C16TAB) with varying amounts of trimethylbenzene (TMB) and triethylbenzene (TEB), whereas drastic structural changes were observed with triisopropylbenzene (TIPB). Characterization by X-ray diffraction and transmission electron microscopy observation revealed that the mesophase was changed from hexagonal p6mm to cubic Pm3n to cubic Fm3m with increasing amounts of TIPB. Thus, the addition of TIPB leads to the preferential formation of spherical micelles rather than the swelling of rodlike micelles. When tetradecyltrimethylammonium bomide (C14TAB) was used, similar structural changes were triggered by smaller amounts of TIPB; however, almost no structural change was observed when octadecyltrimethylammonium bromide (C18TAB) was used. These findings provide a better understanding of the roles of 1,3,5-trialkylbenzenes in the structural control of silica-alkyltrimethylammonium mesophases.

A multifunctional role of trialkylbenzenes for the preparation of aqueous colloidal mesostructured/mesoporous silica nanoparticles with controlled pore size, particle diameter, and morphology

“…In terms of pore size, TIPB is incorporated into micelles of surfactants, as reported previously. [76][77][78][89][90][91] In terms of particle diameter, the decrease in the hydrolysis rate of alkoxysilanes leads to particle growth more dominant than nucleation. 80,82 In the present case, the interaction of TPOS with TIPB due to hydrophobic interactions should inhibit the contact of TPOS with water.…”

“…The reason for the difference in the enlargement of the pore size among various kinds of trialkylbenzenes was discussed in the previous report by Fukuoka et al 91 It is described that in the case of mesoporous silica made from CTAB micelles and trialkylbenzenes, the position of trialkylbenzenes in micelles is a key factor for pore size enlargement. On the basis of this report, the behavior of the formation of micelles is described as follows.…”

Fabrication of core–shell structured mesoporous silica nanospheres with dually oriented mesochannels through pore engineering

“…Since its rst use as a swelling agent for MCM-41 in 1992, 26 1,3,5-trimethylbenzene (TMB) and its analogues have been widely employed for controlling the pore diameters, mesostructures and morphologies of mesoporous materials. [27][28][29][30][31][32] For the rst time, we investigate in the present study the mesochannel orientation control that occurs during the TMB-assisted synthesis process.…”

Swelling of Ionic and Nonionic Surfactant Micelles by High Pressure Gases

“…Causse et al 36 showed that tributylphosphate was able to swell a number of Pluronic surfactant solutions used to make mesoporous silica materials due to its affinity for the hydrophobic core of the micelles. The addition of trimethylbenzene during the synthesis of mesoporous silica was also seen to result in material with enlarged pores, as reported by Chen et al 37 The addition of the swelling agent triisopropyl benzene during the synthesis of CTAB-templated mesoporous silica resulted in swollen 2D hexagonal system as reported by Fukuoka et al 38 With increasing amounts of triisopropyl benzene during the synthesis, a phase change from 2D hexagonal to a cubic system was observed. Blin et al 39 studied the affect of alkane addition on the synthesis a of CTAB-templated mesoporous silicas; decane was found to be the most successful swelling agent of CTAB in that study.…”