Novel block copolymer templates for tuning mesopore connectivity in cage-type mesoporous silica films

Abstract

Mesoporous silica films with large spherical mesopores are synthesized using new laboratory-made polystyrene-block-polybutadiene-block-polystyrene based triblock copolymers in which the polystyrene block is functionalized with hydrophilic sulfonic groups. When the relative weight of the copolymer to silica source is in the range from 10 to 70 mass%, spherical mesopores with uniform sizes can be formed in the films. In addition, when the ratio is lower than 20 mass%, spherical mesopores are separated by thick silica walls in the films. Nevertheless, owing to the presence of small-sized mesopores in the silica walls, all the spherical mesopores are accessible from the outside. With the gradual increase of the chosen copolymer/silica ratios, the distance between neighboring mesopores is reduced without a significant change of the original mesopore size, which has not been observed in previous reports using other block copolymers as templates.