Influence of the adjustable parameters of the DPD on the global and local dynamics of a polymer melt

We present DPD simulations of linear polyethylene melts with force fields derived from microscopic simulations using the concept of potential of mean force. We aim at simulating realistic short polymers from a qualitative and quantitative point of view. An interesting issue is then to know the influence of the adjustable parameters of the DPD: γ, the friction coefficient, and rC, the cut-off radius, on the global and local dynamics of the polymer, i.e., the diffusion coefficient, DCM, the end-to-end decorrelation time, τR and the Rouse times. By varying these two parameters, we investigate structural and dynamical properties for different polymeric systems at a given chain length. Although scaling laws typical of the Rouse model have been reproduced using this DPD method, we observe deviation from the Rouse theory for the local dynamics of certain systems. The dynamical properties of the polymer melt are defined simultaneously by γ and rC. Therefore we combine these two parameters, introducing a new parameter, the effective friction coefficient, γeff.