Investigating the influence of different thermodynamic paths on the structural relaxation in a glass-forming polymer melt

Abstract

We present results from molecular dynamics simulations of the thermal glass transition in a dense polymer melt. In previous work we compared the simulation data with the idealized version of mode-coupling theory (MCT) and found that the theory provides a good description of the dynamics above the dynamical critical temperature. In order to investigate the influence of different thermodynamic paths on the structural relaxation (α-process), we performed simulations for three different pressures and are thus able to give a sketch of the critical line of MCT in the pressure-temperature plane, where, according to the idealized version of MCT, an ergodic-nonergodic transition should occur. Furthermore, by cooling our system along two different paths (an isobar and an isochor), with the same intersection point of the critical line, we demonstrate that neither the dynamical critical temperature nor the exponent γ depend on which path is chosen.