Morphology Development of Mesoporous Materials: a Colloidal Phase Separation Mechanism

Abstract

Synthetic conditions such as temperature, stirring rate, ionic strength, acidity, and reactant ratios that affect the mesostructures and macrostructures of mesoporous materials have been extensively studied in the nonionic block copolymer templating system. Highly ordered SBA-15 materials with ∼100% rodlike morphologies (∼1−2 μm long) have been obtained in the presence of inorganic salts. Synthesis conditions such as low temperature, low acidity, and low ionic strength that increase the induction time give rise to the morphologies of mesoporous silica with increased curvatures. The particle growth process of rodlike SBA-15 materials from solutions has been examined by directly observing the morphologies of particles as a function of time. A colloidal phase separation mechanism (CPSM) for the formation of mesoporous materials is proposed. It is suggested that the formation process of mesoporous materials involves three stages: (1) cooperative self-assembly of inorganic/organic composites; (2) formation of...