Melt Viscoelasticity

Abstract

It is difficult to treat polymer dynamics such as those of rheology in a molecular simulation because an unfeasibly long calculation is required to reach the equilibrium state. However, coarse-grained polymer molecules can be used to treat chain entanglement directly. In the study described in the present chapter, the coarse-grained bead–spring model as an analogy of a real polymer chain was applied to an actual polymer material to determine its rheological characteristics. In addition, the autocorrelation function of stress was calculated concurrently with a simulation to reduce the memory requirement. The entanglement molecular weight and various relaxation times obtained by calculation using COGNAC were in agreement with the literature data. By comparing the entanglement and relaxation times obtained from calculation using the rheological properties of real polymer materials, useful information on melt viscoelasticity can be obtained from relative values.