A Study on the Effect of Template Chain Length on the Synthesis of Mesoporous Silica in An Acidic Condition

Abstract

Hexagonal mesoporous silica materials were synthesized in an acidic medium using different chain length of the quaternary ammonium surfactants as a template. The effects of chain length on the physical property, morphology of mesoporous materials, and the temperature on synthesis of materials in C n TMBr-TEOS-HNO 3 -H 2 O (n 5 12,14,16,18) system were systematically studied. The synthesized products were characterized by X-ray diffraction patterns, scanning electron microscopy, transmission electron microscopy, and nitrogen sorption analysis. It was found that degree of ordering, the d spacing values, and pore size all increase with an increase in the chain length of the template. The optimum synthesis temperature for mesoporous silica using C 18 TMBr-TEOS-HNO 3 -H 2 O system is slightly higher than the Krafft point. The temperature and pH can all affect the expandability of micelles, and so an increase in temperature and decrease in pH all lead to an increase in the pore size. It is also found that the shear flow and chain length are two key factors inducing the formation of millimeter-scaled silica ropes and micrometer-scaled rope fibers.

Design Rules for Mesoporous Silica toward the Nanosize: A Systematic Study

“…As expected from the decrease of particle size, the surface area of the samples, which was maximum at pH 11.6, generally increased with respect to the previous series. This is an indication that lower pH has influence also on the micelle organization structures, producing effects similar to those already discussed in the literature and related to the use of different surfactants or silica sources with varied alkyl-chain length. ,, …”

Pore ordering in mesoporous matrices induced by different directing agents

“…The pore sizes and the lattice periodicity depend primarily on the type of the surfactant [12,18], but also organic co-solvents can affect the pore size acting as spacers inside the micelles [19]. Thus, ethoxyethanol acts not only as solvent but also as co-surfactant, controlling the morphology and pore structure.…”

Hybrid mesoporous silica with controlled drug release

“…At low magnification, all samples show the typical particle shapes of the ordered mesoporous silica prepared in acidic conditions. 6 They appear as folded or twisted rope fibres at lower magnification (Fig. 4).…”

“…5 The degree of ordering and the pore size can be changed by varying the chain length of the surfactant molecule, or using co-solvent additives. 6,7,8 Another way to manipulate the pore structure and the pore surface is to use mixed precursors. The attempts of using methylsilane as partial substituent for TEOS resulted in the increase of the surface area, to the significant decrease of the pore size and to the broadening of the pore size distribution.…”