Diffusivity and glass transition of polymer chains in polymer nanocomposites

Abstract

The diffusivity and glass transition of polymer chains in polymer nanocomposites are studied by using dynamic Monte Carlo simulation. Nanoparticles are modeled as immobile and distributed in a cubic lattice in the system. The diffusion coefficient D of polymer chains is reduced, while the glass transition temperature T_g is increased by nanoparticles. Our results show that the effect of nanoparticles can be summarized as D = D₀[1 − exp(−α·ID/2R_g)] and T_g = T_g,0[1 − exp(−α·ID/2R_g)]⁻¹, with D₀ and T_g,0 being the diffusion coefficient and the glass transition temperature in the absence of nanoparticles, R_g the radius of gyration of polymer chains, and ID the surface spacing between nearest-neighbor nanoparticles. The parameter α that governs the dynamics of polymer chains decreases with increasing nanoparticles’ size or decreasing the temperature. Our results also show that smaller nanoparticles exert a stronger influence on the polymer dynamics at the same concentration of nanoparticles, whereas larger nanoparticles show a stronger effect at the same ID.