Tuning the structure and the mechanical properties of epoxy–silica sol–gel hybrid materials

Abstract

A new route for the synthesis of a monolithic porous hybrid organic–inorganic material composed of silica and an epoxy resin is reported. This ormosil material is prepared by supercritical drying of a gel obtained by a one-pot procedure and using ethanol as the only solvent. The microscopic analysis reveals that the material presents an open network of micrometric pores. The characteristics of the pore structure strongly depend on the ratio between silica and epoxy. While in most cases the structure is formed by homogeneous hybrid primary particles, a foam-like structure is observed for a specific composition, which seems related to a phase-separation effect. The material presents rubber-like behavior under compression. Moreover, the compression modulus can be continuously tuned along two orders of magnitude through the variation of the silica–epoxy ratio, allowing the preparation of a material with tailored mechanical properties.