Syntheses of High-Quality Mesoporous Materials Directed by Blends of Nonionic Amphiphiles under Nonaqueous Conditions

Abstract

A rapid solvent evaporation approach combined with the blends of nonionic amphiphiles as the structure-directing agents (SDA) has been demonstrated to direct the formation of high-quality mesoporous silica materials with two-dimensional (2D) hexagonal or 3D cubic mesostructures. By using oligometric alkyl-ethylene oxide surfactant Brij 35 (C12H25EO23) as a co-template, high-quality hexagonal (p6m) mesoporous silica can be prepared by using triblock poly(ethylene oxide)- b-poly(propylene oxide)-b-poly(ethylene oxide) co-polymer Pluronic P123, EO20PO70EO20, as a template in ethanol media. A highly ordered cubic (space group Im3m) mesoporous silica is obtained by using poly(ethylene oxide)-b-poly(butylene oxide)- b-poly(ethylene oxide) co-polymer polyglycol B50-6600, EO39BO47EO39, as a template and Brij 35 as a co-template. The SDA composed of triblock co-polymer and a small amount of nonionic surfactant can increase the efficiency of assembly of organic and inorganic hybrid species and result in the quality improvement of the silica mesostructure. Interestingly, by using B50-6600 mixed with a large amount of Brij 35 as the SDA, a limited mesophase transition from cubic (space group Im3m) to 2D hexagonal (p6m) is first observed. Generally, the amphiphile blend approach can increase the total pore volumes, BET surface areas of the mesoporous materials, and reduce their microporosities.