A simulation study on the effect of nanoparticle size on the glass transition temperature of polymer nanocomposites

The effect of the size of nanoparticles, sigma(NP), on the glass transition temperature, T-g, of polymer nanocomposites is studied by using molecular dynamics simulations. The variation of T-g with sigma(NP) shows two distinct behaviours for polymer nanocomposites at low and high volume fractions of nanoparticles (f(NP)). At a low f(NP), T-g decays almost exponentially with sigma(NP), whereas at a high f(NP)T(g) shows a complex behaviour: it initially increases and then decreases with increasing sigma(NP). The decrease in T-g with sigma(NP) is due to the significant decrease of adsorbed polymer monomers, while the increase in T-g with sigma(NP) is attributed to the slower diffusion of larger nanoparticles. We have also investigated the diffusion and relaxation of polymer chains at a temperature above T-g for both low and high f(NP)s. The diffusion constant and relaxation time of polymer chains are highly consistent with the behaviour of T-g.

Automated summary

The effect of nanoparticle size on the glass transition temperature of polymer nanocomposites shows a complex behavior, with T-g decaying almost exponentially at low nanoparticle volume fractions and exhibiting a more varied pattern at high volume fractions. The decrease in T-g is attributed to reduced adsorbed polymer monomers, while the increase is linked to slower diffusion of larger nanoparticles. The diffusion constant and relaxation time of polymer chains are closely related to T-g behavior.