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 (SLLS) 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 scattering theory from a capillary wave. As the polymer concentration increases, the solution viscoelasticity is found to play an important role in affecting the dynamics of surface waves. By comparing experiment with theory, a clear-cut capillary wave to elastic wave evolution in the PIB/decane solution is found. The nature of the quasielastic peak that appears in the SLLS spectrum of the viscoelastic polymer solution is delineated. (C) 1998 American Institute of Physics.