Thermodynamic and structural properties of polystyrene/C60 composites: A molecular dynamics study**Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0200902), Science and Technology Commission of Shanghai Municipality, China (Grant No. 17JC1400801), and Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 51705369).

Abstract

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 Tg 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 Tg (rubbery region). However, the CTE decreases with increasing content of C60 below Tg (glassy region).