A composition transferable and time-scale consistent coarse-grained model for cis-polyisoprene and vinyl-polybutadiene oligomeric blends

Abstract We study a coarse-grained model for a binary blend system composed of cis-polyisoprene and vinyl-polybutadiene. Since the slow relaxation dynamics of polymers may require very long simulation times, coarse-grained descriptions are regularly used in order to reduce computational cost while keeping the essential physics. Relaxation dynamics of a coarse-grained model is sometimes accelerated by the smooth coarse-grained potentials. However, the magnitude of the acceleration may be different in different components in a multi-component system. In order to simulate a time-scale consistent dynamics, the acceleration effects should be the same across the different components. Here, we investigate a time-scale consistent coarse-grained model for a binary polymer blend. For the coarse-grained equation of motion, we adopt the Langevin equation and adjust the friction coefficients by focusing on the relaxation times of the first normal mode of the polymers. A united-atom model is used as a reference system of the coarse-graining. Since it is found that the solubility parameter of the atomistic model is much larger than the experimental result, our simulation model is not applicable for the quantitative predictions, but we utilize it as a example system to study a time scale mismatch of a coarse-grained model. We find that the coarse-grained potentials and the friction coefficients derived for one blend composition captures different compositions of the blend. Furthermore, it is found that the magnitude of the acceleration effects of the blend rarely depends on the composition ratio. This implies that our coarse-grained model can be used for inhomogeneous systems.