Effect on Thermal and Mechanical Properties of Polystyrene Chain Grafting on Silica Nanoparticles

Thermal and rheological analysis of a silica - grafted polystyrene nanocomposite sample is carried out using the differential scanning calorimerty (DSC) and the rheometry. Measured properties are compared to those of a neat polymer of similar molecular weight. At 20% silica loading, the glass transition temperature of the nanocomposite is increased by 1.2 K and the step change in heat capacity (ΔC_p) at the T_g for the nanocomposite is found to be reduced by 9%, indicating reduced segmental mobility of the grafted polymer chains. Absolute C_p measurements similarly show a decrease in both the glassy and liquid heat capacity values, with a decrease of 11% in absolute C_p observed at T_g. The viscoelastic response of the nanocomposite also changes significantly upon nanoparticle addition. The plateau modulus (G_N⁰) is found to be increased by at least 30% as compared to the neat polymer sample and a shift of the terminal flow regime to lower frequencies is observed. Experiments in the glassy regime are in progress.