An improved dissipative particle dynamics model for simulation of entangled polymers

We develop an improved polymer model to capture entanglements within the DPD framework by using simplified bond-bond repulsive interactions to prevent bond crossings. We show that structural and thermodynamic properties can be improved by applying a segmental repulsive potential (SRP) that is a function of the distance between the midpoints of the segments, rather than the minimum distance between segments. The alternative approach, termed the modified segmental repulsive potential (mSRP), is shown to produce chain structures and thermodynamic properties that are similar to the softly-repulsive, flexible chains of standard DPD. Parameters for the mSRP are determined from topological, structural and thermodynamic considerations. The effectiveness of the mSRP in capturing entanglements is demonstrated by calculating the diffusion and mechanical properties of an entangled polymer melt. This improved DPD method was used in simulations for entangled polymer networks to explore impact of branched architectures on the mechanical response to the tensile and compressive deformation.