The mechanical and structural responses of
hydroxyl-terminated cis-1,4-polybutadiene melts to
shock waves were investigated by means of all-atom non-reactive molecular dynamics simulations. The simulations were performed using the OPLS-AA force field but with the standard 12-6 Lennard-Jones potential replaced by the Buckingham exponential-6 potential to better represent the interactions at high compression. Monodisperse systems containing 64, 128, and 256 backbone
carbon atoms were studied. Supported
shock waves were generated by impacting the samples onto stationary pistons at impact velocities of 1.0, 1.5, 2.0, and 2.5 km s(-1), yielding
shock pressures between approximately 2.8 GPa and 12.5 GPa. Single-molecule structural properties (squared radii of gyration, asphericity parameters, and orientational order parameters) and mechanical properties (density,
shock pressure,
shock temperature, and shear stress) were analyzed using a geometric binning scheme to obtain spatio-temporal resolution in the reference frame centered on the
shock front. Our results indicate that while shear stress behind the
shock front is relieved on a ∼0.5 ps time scale, a
shock-induced transition to a glass-like state occurs with a concomitant increase of structural relaxation times by several orders of magnitude.