  The shock initiation of energetic materials is mediated by the localization
of mechanical energy into hotspots. These originate through the interaction of
the shock and material microstructure; the most potent hotspots are formed by
the collapse of porosity. Recent work using molecular dynamics (MD) has shed
light on the molecular mechanisms responsible for the shock-to-deflagration
transition following pore collapse in pure energetic materials. However,
explosive formulations are composites of energetic crystals and a polymer
binder, which differs from the prior focus on pure materials. The role of
polymer phases on hotspot formation and its criticality is not well-understood.
We use reactive MD simulations to investigate the role of polystyrene and
polyvinyl nitrate films around pores in the shock-induced pore collapse of RDX.
The polymer affects the hotspots' temperature and their criticality. While the
presence of inert polymer often delays or hinders chemical reactions of the
energetic material, certain geometries accelerate chemistry. The simulations
provide a mechanistic understanding of these phenomena.
