The presence of various counteranions at the interfacial region of the silicate-surfactant mesophase introduces opportunities for manipulation of the phase structure. Well-ordered 3D-hexagonal P63/mmc, cubic Pmn, 2D-hexagonal p6mm, and cubic Iad mesoporous materials have been synthesized with the same surfactant, cetyltriethylammonium bromide, in the presence of various acids. The counteranions of acidic media have resulted in increasing the surfactant packing parameter g in the order SO42- < Cl- < Br- < NO3-, which leads to the different time course of formation of mesostructures. The effect of counteranions on the formation of mesostructures is explained in terms of not only the adsorption strength on the headgroups of the surfactant micelle but also the rate of silica condensation affecting the charge density matching between the surfactant and silica. It has been found that the mesophase is always transformed from the larger g parameter into the smaller one. The distinct morphologies of the 3D-hexagonal P63/mmc mesophases have been rationally explained by supposing this particular mesostructure. The cubic Iad phase has been first synthesized under acidic conditions.

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The presence of various counteranions in the interfacial region of the silicate−surfactant mesophase introduces opportunities for manipulation of the phase structure. Well-ordered three-dimensional hexagonal P63/mmc, cubic Pm3̄n, two-dimensional hexagonal p6mm, and cubic Ia3̄d mesoporous materials have been synthesized with the same surfactant (cetyltriethylammonium bromide), depending on the kind of acids. The counteranions of acidic media have resulted in increasing surfactant packing parameter g in the order SO4 2- < Cl- < Br- < NO3 -, which leads to different formation routes to the mesostructures. It has been found that the mesophases are always transformed from the lower curvature one into the higher curvature one in the acidic synthesis gel. The combination of X-ray diffraction patterns, scanning electron microscope images, and high-resolution transmission electron microscope images presented visible evidence for the mesostructural constructions. In particular, the synthesis of a cubic Pm3̄n mesoporous molecular sieve was studied in the presence of trimethylbenzene (TMB) isomers. The rate of transformation is greatly affected by the structure of the TMB isomers and their content; 1,2,3-TMB was the most favorable to the stabilization of the p6mm hexagonal mesophase, 1,3,5-TMB was the least favorable, and 1,2,4-TMB showed intermediate behavior.