Ring-Filling Effect on Stress–Strain Curves of Randomly End-Linked Tetra-Arm Prepolymers

Abstract

To clarify the stress–strain relation of polymer networks filled with ring polymers, we investigated randomly end-linked networks produced by a pseudo-crosslinking process of tetra-arm prepolymers through coarse-grained molecular dynamics simulations of the Kremer–Grest model. We considered three types of systems: (1) randomly end-linked network without rings, (2) randomly end-linked network with superimposed rings, and (3) randomly end-linked network made from a blend of rings and tetra-arm prepolymers. First, the properties of the network structure (without rings) were investigated, revealing that the prepolymer concentrations affect the entanglement properties of networks. Next, we investigated the effect of rings on the networks because the ring polymers do not form bonds with the network but introduce topological constraints by chain penetration through rings. To characterize the chain penetration, we developed a novel method combining the chain shrinking process and the classification of the ring shape. The shape of the ring with multiple chain penetration was significantly altered by uniaxial stretching. We confirmed that rings with multiple chain penetrations enhanced or reduced the stress in the stress–strain curve depending on the underlying network structures and rings with or without penetrations of strands. These findings contribute to the material design of crosslinked rubbers filled with rings to control mechanical properties.