Molecular dynamics simulation of collinear polymer nanoparticle collisions: Reaction and scattering

Collinear collisions of polyethylene nanoparticles are studied, with a particular emphasis on the transition between sticking and reactive scattering trajectories. The former are characterized by collisions where the two polymer particles form a particle dimer, the latter by collisions resulting in the gross change of particle structure, such as particle fragmentation or transfer of polymer chains from one particle to another. It is observed that in the collinear case there are no scattering trajectories where the particles undergo nearly elastic collisions and rebound with small energy change. This property is attributed to the fact that during the collision process the particles undergo reorganization, and the energy involved is difficult to recover. The result is that at all but extremely high velocities, particles undergo rapid and irreversible energy transfer from the relative translational coordinate into other internal coordinates, resulting in dimerization of the polymer particles.