Molecular dynamics simulation of microscopic deformation of cross-linked isoprene rubber networks

Molecular dynamics analysis is wildly used to investigate the interaction between molecular chains, comprehensively and intuitively reveal the structure of a network and its deformation characteristics. The use of molecular dynamics can reveal the relationship between microstructural changes and macroscopic deformations of materials, which has an important impact on the mechanical properties of rubber. Using molecular dynamics simulation, three coarse-grained models of isoprene rubber (IR) with different degrees of cross-linking were established and subjected to uniaxial stretching. The positions of the effective cross-linking points in the cross-linked IR network during deformation were derived, and compared with their corresponding affine deformation positions. It is found that the average deviation value of cross-linked IR crosslinking points in the stretching direction is larger than that in the lateral directions. The larger the degree of crosslinking, the stronger the macroscopic affine relationship of the crosslinking points. The relative deviation increases with the increase of the stretching rate, and the relative deviation perpendicular to the stretching direction is larger than that in the stretching direction. The end-to-end distances of the single molecular chains in the IR molecular chain network are compared with the end vectors and their affinities to search for cross-linked IR macroscopic deformation versus the microscopic deformation of the cross-linked network. It is found that the length deviation of the cross-linked IR end-to-end distances from the affine deformation in the stretching direction under uniaxial stretching is larger than that perpendicular to the stretching direction; and the direction deviation of the end vector direction from the affine deformation in the stretching direction is larger than that in the stretching direction.