Heterogeneous Chain Dynamics in a Supercooled Polymer Melt: Relaxation Mode Analysis Study

Abstract

The conformational relaxation of a polymer in a supercooled melt consisting of short flexible polymers is studied by molecular dynamics simulations. Relaxation mode analysis (RMA) is used to examine the dynamics of polymers in the melt. To analyze the dynamics around a local minimum of free energy, the simulation time at low temperatures is chosen to be of the same order as the longest relaxation times of polymers, and the simulation is repeated many times to generate an isoconfigurational ensemble. As the temperature is lowered, a slowing down of relaxation and a broadening of the relaxation rate spectrum are observed. Not only the conformation of each polymer fluctuates heterogeneously but also its dynamics deviates from that expected from the Rouse model. These results are direct evidence of dynamic heterogeneity in terms of conformational relaxation.