Collision dynamics and surface wetting of nano-scale polymer particles on substrates

Classical trajectory calculations are used to study collisions of nano-scale polyethylene (PE) particles on Si, C, and Al surfaces in a vacuum. The PE particles generated with up to 12 000 atoms have been propagated up to 100 ps for those surfaces to investigate the self-organization of polymer particles (mechanical memory) via collisions. It is shown that particles with the initial velocity greater than 8 Å/ps lose some chains while spreading on (coating) the surfaces during impact. In the simulation, the nano-scale PE particles with the initial velocity less than 5 Å/ps can self-organize back to their original spherical shape and do not show deformation of the shape. The results suggest that the experimentally observed deformation of a polymer particle on a substrate is due mainly to the surface interaction between the polymer particle and the substrate (surface wetting) and not to the collision.