CLEAR-CUT EXPERIMENTAL-OBSERVATION OF THE CAPILLARY WAVE TO ELASTIC-WAVE CROSSOVER IN CONCENTRATED POLYMER-SOLUTIONS

A detailed experimental study of the surface laser light scattering (S LLS) spectrum of the polyisobutylene (PIB)/decane solution over a wide range of polymer concentration is carried out. In the dilute solution , the SLLS spectrum is found to be described adequately by a scatterin g theory from a capillary wave. As the polymer concentration increases , the solution viscoelasticity is found to play an important role in a ffecting the dynamics of surface waves. By comparing experiment with t heory, a clear-cut capillary wave to elastic wave evolution in the PIB /decane solution is found. The nature of the quasielastic peak that ap pears in the SLLS spectrum of the viscoelastic polymer solution is del ineated. (C) 1998 American Institute of Physics.