Looking the dynamical heterogeneity in supercooled polymer system through Isocongurational ensemble

CRISTIAN BALBUENA; MELISA GIANETTI; SOULÉ, EZEQUIEL RODOLFO

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 2018 vol. 149

0021-9606

The dynamic correlations that emerge in a polymer system in the supercooling region have been studied using Molecular Dynamic simulations. It is known that when a glass former approaches the glass transition temperature, the dynamics of the system (in terms of the mobilities of the particles) not only signicantlyslows down, but also becomes more heterogeneous. Several theories relate this slowing down to increasing spatial correlations (structural), for example through the appearance of cooperative relaxation regions in the Adam-Gibbs theory. In this work we employ Pearson´s coecient in isocongurational ensemble (ICE) which allows us to study the dynamic correlations of the monomers in the ICE and establish the relation between the structure of the monomers and its dynamic behavior. Similar to what happens with mobility, monomers with highest correlation are clustered, and the clustering increases with decreasing temperature. An interesting result is that regions with high ICE dynamic correlation are not coincident with highly mobile or immobile regions. This results represents a new approach to the study of dynamic heterogeneity that emerges in a glass forming liquids, complementing the more traditional characterization in terms of mobility. The methodology proposed in this work that characterize the connected dynamic regions to structural causes can represent an alternative way to observe the cooperative relaxation regions.