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

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