Thermodynamic and structural properties of polystyrene/C₆₀ composites: A molecular dynamics study

To tailor properties of polymer composites are very important for their applications. Very small concentrations of nanoparticles can significantly alter their physical characteristics. In this work, molecular dynamics simulations are performed to study the thermodynamic and structural properties of polystyrene/C₆₀ (PS/C₆₀) composites. The calculated densities, glass transition temperatures, and coefficient of thermal expansion of the bulk PS are in agreement with the experimental data available, implying that our calculations are reasonable. We find that the glass transition temperature T_g increases accordingly with an added concentration of C₆₀ for PS/C₆₀ composites. However, the self-diffusion coefficient D decreases with increase of addition of C₆₀. For the volumetric coefficients of thermal expansion (CTE) of bulk PS and PS/C₆₀ composites, it can be seen that the CTE increases with increasing content of C₆₀ above T_g (rubbery region). However, the CTE decreases with increasing content of C₆₀ below T_g (glassy region).