With experimental investigations and current theories, molecular modeling became an inevitable technique to study the perplexing phenomenon of glass transition. Among polymers, small variations in atomic interactions yield different values of the glass transition temperature, T{g}. To reveal the influence of differences in the atomic functionality on the value of T{g}, and thus to probe the molecular mechanisms responsible for this transition, atomistic simulations have to be undertaken. However, such simulations are argued not to accurately represent physically the glass transition due to the long relaxation times involved. Here we show the universality of the well-known Williams-Landel-Ferry equation for the experimental thermal dependence of polymer viscosities as demonstrated with atomistic simulations. Consequently, atomic aspects could be explicitly revealed. The contribution of atomistic simulation to the study of glass transition is thus confirmed. However, it has to be used complementarily with experiments and coarse-grained simulation to reveal the atomic aspects of current theories.

Many efforts in experimental and theory are dedicated to study the puzzling problem of glass transition. With the involvement of molecular modeling, a fresh look at this intricate phenomenon was taken. Nevertheless, the difficulty to accurately probe all the domains of times necessary to describe this process still remains. Moreover, using a full-atomic description to account for equilibrated systems has been called into question. However, such depiction offers a special regard since it could deal with small modifications in the polymer architecture. From an appropriate selection of phase space, it was shown that atomistic simulation was able to link simulated and experimental glass transition temperatures of vinylic polymers using the established Williams-Landel-Ferry equation. Consequently, atomic insight into the glass transition phenomenon can be gained from a comparison of simulated data with actual models and experimental data. In this paper, the different parameters intervening in the Vogel-Fulcher-Tamman equation stemming from the local dynamics of a series of vinylic polymers are thus compared. Their behavior yields an atomistic viewpoint of the Adam-Gibbs model.

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