Molecular dynamics simulation of shock compressed cis-polybutadiene : from in situ synthesis to mechanical analyses of long-term relaxation processes

We used a recently devised procedure based on molecular dynamics to generate cis-polybutadiene melts with various chain lengths [1] and study their mechanical behaviour under shock compression with the non-reactive OPLS all-atom force-field. The resulting samples show properties in excellent agreement with previous works [2] with negligble influence of the chain length. Comparison of direct shock with shock equilibrium (hugoniostat) simulations shows a discrepancy in the shear stresses. Based on a careful mechanical analysis of the time-dependance of this difference behind the shock front, we show that their timescale is compatible with the typical equilibrium relaxation times at play in these complexe materials.

References
[1] C. A. Lemarchand, D. Bousquet, B.Schnell, N.Pineau, J. Chem. Phys. 150, 224902 (2019)
[2] Markus G. Fröhlich, Thomas D. Sewell, and Donald L. Thompson J. Chem. Phys. 140,024902 114:16, (2014)