Supercritical CO2–organosilane mixtures for modification of silica: Applications to epoxy prepolymer matrix

• Development of a new clean surface treatment of silica nanoparticles.
• Use of ionic liquids as an activator of silanol groups to increase the grafting density of silica.
• Improvement of nanocomposite final properties.

This work is focused on the use of supercritical carbon dioxide (ScCO2) as an environmentally friend process to improve the surface functionalization of silica nanoparticles with amino- and perfluoro-silanes. Here, we combine the use of a phosphonium ionic liquid which plays a role of an activator of silanol groups in ScCO2 to increase the grafting density of silane agents on silica. Then, diglycidyl ether of bisphenol A (DGEBA)-based epoxy nanocomposites filled with different amount of new functionalized silicas (1, 2.5 and 3.5 phr) are prepared and characterized by dynamic-mechanical analysis, transmission electron microscopy and small-angle X-ray scattering. Finally, the treated silica/epoxy systems exhibit better mechanical properties (+30%) when compared to neat epoxy.