Simulation of Elastomers by Slip-Spring Dissipative Particle Dynamics

We study elastomeric networks using dissipative-particle-dynamics simulations. This soft-core method gives access to mesoscopic time and length scales and is potentially capable to study complex systems such as network defects and gels, but the unmodified method underestimates topological interactions and can only model phantom networks. In this work, we study the capability of slip springs to recover topological effects of network strands. We show that slip springs with a restricted mobility restore the topological contributions of trapped entanglements. Uniaxial strain experiments give access to the cross-link and entanglement contribution to the shear modulus of a slip-spring model network. We find these contributions to coincide with those reported for comparable hard-core Kremer-Grest networks (Gula et al. Macromolecules 2020, 53, 6907-6927). For network strands longer than the chains' entanglement length, the contribution of slip springs to the shear modulus equals the plateau modulus of the un-cross-linked precursor melt. However, a constant number of slip springs overestimates the shear modulus for high cross-link densities. To probe their applicability, we successfully compare our simulations with experimental polyisoprene rubbers: a network obtained by parameter-free cross-linking of a simulated polyisoprene melt reproduces the viscoelastic moduli of experimental rubbers.