A New Minimal Surface and the Structure of Mesoporous Silicas

Abstract

The formation of complex inorganic superstructures in nature relies on the interaction between organic and inorganic species to direct the inorganic form away from its “usual” morphology. During synthesis the superstructures are soft and dynamic which makes a study of the nature of the ephemeral interface difficult. [1] However, the inorganic skeletons formed are stable and consequently amenable to detailed examination. In 1992 researchers at Mobil [2] and in Japan [3] made the remarkable discovery that the subtle forms of mesoscopic organization of surfactant molecules could be imprinted on oxide structures. Herein we report our studies of the structure of the surfactant-templated, cubic, mesoporous silica superstructure, SBA-1 [3] and provide a formulation in terms of curvature that has important repercussions for both surfactant structures and the mechanism of formation of inorganic replicas. We establish that the crucial interface that determines the inorganic structure is between the silica and water adsorbed at the micelle surface, not between silica and surfactant, thus challenging the present synthesis mechanisms. [4] We adopt a general protocol for understanding the surface curvature and energy which could be applied widely