Hugoniostat and Direct Shock Simulations in cis‐1,4‐Polybutadiene Melts

Abstract

The non‐reactive OPLS‐AA force‐field is used to compare direct shock and Hugoniostat simulations of a melt of cis‐1,4‐polybutadiene at different shock velocities and with chain lengths up to 500 monomers. Both methods yield equivalent Hugoniot data with negligible influence of the chain length. However, it is found that the dynamical compression effects induce a time‐dependent anisotropy in the stress tensor in the direct shock simulations, yielding a non‐zero shear component. This anisotropy vanishes to the usual isotropic stress through two specific relaxation mechanisms: a fast process (characteristic time ≈1 ps) associated with the relaxation of the local intramolecular degrees of freedom of the chains, and a second slower process (characteristic time ≈100 ps) associated with the structural reorganisation of the polymer chains, involving long‐range intramolecular and intermolecular interactions. A third potential relaxation process, associated with entanglements, may be at play but is beyond the scope of the present study.

Shock compression of semiflexible polymers

“…23 Using molecular dynamics simulations the shock response of several systems were analyzed, including segmented polyureas and polyurethanes, 11,24–26 crystalline polymers, 15,27,28 block copolymers, 11,12 and amorphous systems. 29–33…”

“…23 Using molecular dynamics simulations the shock response of several systems were analyzed, including segmented polyureas and polyurethanes, 11,[24][25][26] crystalline polymers, 15,27,28 block copolymers, 11,12 and amorphous systems. [29][30][31][32][33] In the present study, we focus on the shock compression of semiflexible chains, a topic that remains relatively underresearched compared to other polymer systems. We demonstrate that when semiflexible chains are aligned in the compression direction, the system responds to shock compression through a collective buckling of chains, where the dominant mode diminishes when increasing the compression velocity.…”

Amorphous Cis-1,4-Polybutadiene P-V-T properties from atomistic simulations

“…Over the same range of temperatures and at a cooling rate of 20 K/ns, Dossi et al [19] studied the effect of microstructure on pentamers and decamers of hydroxyl terminated PB using the Dreiding AA force eld. However, to our knowledge, even if different studies have been performed under pressure [20][21][22][23][24][25][26], none of them treated of the effect of pressure on Tg. Indeed, Valega Mackenzie et al [21] studied the mechanical response of copper/polybutadiene joints under stress mixing embedded atom method and Universal AA-FF.…”

“…Indeed, Valega Mackenzie et al [21] studied the mechanical response of copper/polybutadiene joints under stress mixing embedded atom method and Universal AA-FF. Shock-induced structural changes and post-chock relaxations were studied on cis-1,4 polybutadiene melt both using UA-FF [22] and AA-FF force eld [23]. Hooper et al [20] used the Tait EOS to t the PVT data calculated at 298 K for pressure ranging from ambient to 1000 MPa, on a model composed of 40 random copolymer chains composed of 30 units with a microstructure of 40%, 50% and 10% of 1,4-cis, 1,4-trans and 1,2 vinyl units respectively with a UA-FF.…”