Mesoporous silica nanoparticles with an average diameter of $ 20 nm were synthesized by a sol-gel method using binary surfactant system. Polystyrene (PS) composites containing mesoporous silica nanoparticles were prepared by in situ polymerization of styrene monomers. Similar in situ polymerized PS composites were prepared based on the modified silica functionalized with methyl and vinyl groups. The effects of silylation on thermal and rheological properties of the PS/silica composites are investigated. Of particular importance is that the in situ polymerization of monomers within the mesoporous silica may trap some polymer chains, if not all, thereby affording a greater physical interaction between polymer and the porous fillers, whereas the chemical modification of silica surface promotes the polymer-filler interaction, which in turn enhances the thermal stability of composites.

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Fillers are modified with the purpose of increasing their interactions with polymer matrices; however it is necessary to determine the impact that those modifications have on the composite performance and morphology. In this work, the strength of the chemical interactions between silica with different chemical characteristics and acrylonitrile butadiene rubber (NBR) is studied by infrared spectroscopy measuring the increase of C:N fundamental vibration frequency and by density functional theory (DFT) and ab initio methods. The results from the chemical interactions were compared with the morphology and thermal behavior of composites based on those components. Good agreement between the molecular parameters estimated theoretically and the shifting of the absorption frequency due to C:N stretching was observed. Morphological studies revealed that the steric hindrance exerted by modifier moieties on silica surface favors the filler dispersion. Functional groups on the surface strongly interacting with NBR play an important role in the compatibility of immiscible blends of NBR copolymers studied in this work.

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