The mechanical properties and bioactivity of poly(methyl methacrylate)/SiO2–CaO nanocomposite

The mechanical properties and bioactivity of poly(methyl methacrylate)/SiO2–CaO nanocomposite were investigated using dimethyldiethoxysilane (DMDES) and tetraethoxysilane (TEOS), which could produce two and four siloxane linkages, respectively, after a sol–gel reaction. Methyl methacrylate was co-polymerized with 3-(trimethoxysilyl)propyl methacrylate and then co-condensed with DMDES (specimen D) and TEOS (specimen T), respectively, with calcium nitrate tetrahydrate under acidic conditions. The fracture toughness of specimen D was much improved compared to that of specimen T, whereas its fracture strength, hardness, and apatite-forming ability in simulated body fluid (SBF) were slightly decreased. The improved fracture toughness of specimen D without losing apatite-forming ability was explained by the decrease of siloxane linkage numbers and the introduction of alkyl groups in silica structure because covalently bonded siloxane linkages produce hard and brittle fracture behavior in the nanocomposite while the alkyl groups help to make the silica as linear chain structure. The practical implication of these results is that this new nanocomposite can be applied to the filler materials for bone cement and dental composite resin because of its good bioactivity and improved mechanical properties.