Elastomer Mechanics of Cross-Linked Linear-Ring Polymer Blends

Cross-linking a blend of linear and ring polymers creates a new topology-based dual-network elastomer in which the two components differ significantly in their topology. We use molecular simulations and topological analysis to examine key mechanical properties as functions of ring polymer volume fraction ϕ_R. For ϕ_R < ϕ_R^*, where the rings begin to overlap, the network shear modulus <i>G</i> and the maximum stretch ratio λ_p are weakly dependent on ϕ_R. For ϕ_R > ϕ_R^*, entanglements trapped in the network are diluted as the rings overlap, leading to a significant decrease in <i>G</i> and an increase in λ_p with increasing ϕ_R. The peak tensile stress, σ_p, exhibits a maximum around ϕ_R^*, indicating an enhancement of network strength due to the stronger cohesion from the entanglements between linear and ring polymers.