  We report observations of weird but interesting phenomenon from the molecular
dynamics simulations, occurrence of second blows in the head-on collisions of
two equal-sized spherical nano polymer droplets. In the head-on collisions, we
usually expect a single peak of impact forces between two colliding droplets.
But, in the simulations, the second peak of the impact forces is actually
observed. Its underlying mechanisms at the molecular scale are also proposed.
