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

Classical trajectory calculations are used to study collisions of nano-scal e polyethylene (PE) particles on Si, C, and Al surfaces in a vacuum. The PE particles generated with up to 12000 atoms have been propagated up to 100 ps for those surfaces to investigate the self-organization of polymer parti cles (mechanical memory) via collisions. It is shown that particles with th e initial velocity greater than 8 Angstrom/ps lose some chains while spread ing on (coating) the surfaces during impact. In the simulation, the nano-ec ale PE particles with the initial velocity less than 5 Angstrom/ps can self -organize back to their original spherical shape and do not show deformatio n of the shape. The results suggest that the experimentally observed deform ation of a polymer particle on a substrate is due mainly to the surface int eraction between the polymer particle and the substrate (surface wetting) a nd not to the collision. (C) 1999 Elsevier Science B.V. All rights reserved .