Molecular mechanism of material deformation and failure in butadiene rubber: Insight from all-atom molecular dynamics simulation using a bond breaking potential model

摘要

Microscopic details of the tensile behavior of disulfide crosslinked cis-1,4-polybutadiene are unveiled using atomistic molecular dynamics (MD) simulations. Stepwise deformation and relaxation method was employed to determine the tensile behavior and underlying molecular mechanism was clarified by analyzing the MD trajectory. Calculated stress-strain curve well reproduces the experimental observation. We found that tensile behavior of rubber is predominantly correlated to its microscopic structural transformation, which is primarily governed by the crosslinking topology. Strain dependence of the structural transformation due to crosslinking of polymer chains results in hyperelastic tensile behavior of rubber. Rapid increase in the stress for initial strain arises due to the realignment of randomly oriented polybutadiene chains along the pulling direction. For the intermediate strain, polybutadiene chains elongate upon the application of deforming force, giving rise to a gentle increase in the stress. However, elongation of polybutadiene chains is non-uniform due to system topology. This gives rise to the heterogeneity in the system, resulting in formation and of the void. Sharp increase in the stress at large strain can be attributed to extensibility of the polybutadiene chains. Finally, material failure transpires by dissociation of crosslinking chemical bonds.