Toughening of epoxy resin with poly(methyl methacrylate) grafted silica core-shell particles

Structurally well-defined core-shell particles were prepared by modifying the surface of silica with initiators for atom transfer radical polymerization (ATRP), and followed by using these initiator-modified particles as ATRP macro-initiators for methyl methacrylate. These particles were characterized with Fourier-transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM). The tethered polymer chains on the grafted silica particles were cleaved with hydrofluoric acid and measured with gel permeation chromatography (GPC). The results showed that poly(methyl methacrylate) (PMMA) chains grew from the particle surfaces in form of individual particles comprising of a hard silica core and a well-defined, densely grafted outer polymer layer. Diglycidyl ether of bisphenol-A (DGEBA) based epoxy resin was toughened with various doses of the synthesized PMMA-grafted silica particles. Resulting composite materials were characterized by tensile testing, SEM, dynamic mechanical analysis (DMA) and TGA. The results indicated that the incorporation of the core-shell particles improved the toughness of the composites without any significant deterioration of its thermal properties.