MOLECULAR-DYNAMICS SIMULATIONS OF THE THERMAL GLASS-TRANSITION IN POLYMER MELTS - ALPHA-RELAXATION BEHAVIOR

We present molecular-dynamics simulations of the thermal glass transit ion in a dense model polymer liquid. We performed a comparative study of both constant volume and constant pressure cooling of the polymer m elt. Great emphasis was laid on a careful equilibration of the dense p olymer melt at all studied temperatures. Our model introduces competin g length scales in the interaction to prevent any crystallization tend ency. In this first manuscript we analyze the structural properties as a function of temperature and the long time or cr-relaxation behavior as observed in the dynamic structure factor and the self-diffusion of the polymer chains. The ct relaxation can be consistently analyzed in terms of the mode coupling theory of the glass transition. The mode c oupling critical temperature T-c, and the exponent gamma defining the power law divergence of the alpha-relaxation time scale, both depend o n the thermodynamic ensemble employed in the simulation.