We have measured surface morphological changes of polystyrene films using nanosecond time-resolved interferometry. In the case of low molecular weights (3.0 × 10 3 and 5.0 × 10 3 ), the surface contracts exponentially. In the case of high molecular weight (1.0 × 10 6 ), however, two different contraction processes are observed, that is, a major contraction and a minor tail. The thermal diffusion coefficients of major components acquired experimentally from both high and low molecular weights are almost the same as the value in the literature, which indicates thermal diffusion is dominant for a major contraction. On the other hand, we consider the minor tail from the viewpoints of rubber-glass transition and polymer entanglements.
- Laser ablation
- Nanosecond expansion
- Tens of microsecond contraction