PMMA-mesocellular foam silica nanocomposites prepared through batch emulsion polymerization and compression molding

PMMA-mesoporous silica nanocomposites were prepared for the first time through in situ batch emulsion polymerization of methyl methacrylate in the presence of large pore MSU-F silica with a mesocellular foam structure (24.8 nm average cavity size) and subsequent compression molding of the polymer-silica nanoparticle mixtures. For composites containing 5.0 wt % silica, the onset decomposition temperature and the temperature at 10% weight loss for the nanocomposite increased 41 °C and 50 °C, respectively, in comparison to pure PMMA. The glass transition temperature of the nanocomposite increased 9.3 °C, as determined by differential scanning calorimetry. In addition, the storage modulus determined by dynamic mechanical analysis increased 17% and 80% at 50 °C and 100 °C, respectively. Substantial improvements in tensile strength (+50%) and modulus (+72%), were achieve at 10 wt % nanoparticle loading. Composites made by compression molding of physical mixtures of PMMA and MSU-F silica powders provide less improvement in thermal stability, glass transition temperature and mechanical properties in comparison to the composites made through in situ batch emulsion polymerization. Unlike previously reported composites made from nanoclays, the silica composites reported here show improvements in both thermal stability and mechanical reinforcement.