Realistic Coarse-Grain Model of cis-1,4-Polybutadiene: From Chemistry to Rheology

We present a practical coarse-grain (CG) force field for dissipative particle dynamics (DPD) simulations of cis-1,4-polybutadiene (cPB). The parametrization of the model was realized using the recent Bayesian bottom-up scheme based on trajectory matching. The CG force field enables the correct description of cPB melts in a broad range of temperatures and pressures. We demonstrate its robustness by measuring the thermal expansion coefficient and isothermal compressibility consistent with experimental values. By reducing the computational cost by a factor 21 with respect to classical united-atom force fields while keeping accuracy, we can reach larger time and length scales suitable for the investigation of the rheological and the mechanical properties of such polymeric systems. In particular, the rubbery plateau and the entanglement mass for monodisperse cPB entangled melts are quantitatively predicted using this CG model.