Clear-cut experimental observation of the capillary wave to elastic wave crossover in concentrated polymer solutions

Abstract

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.

Surface waves on non-Newtonian viscoelastic liquids

“…This behavior coincides with the quasielastic peak reported in Ref. [16]. Therefore, the modes labeled "c", "b," and "a" correspond to the capillary wave mode, elastic wave mode, and the viscoelastic relaxation mode, respectively, in the case ofσ = 10.0.…”

“…Then, we decompose them further into partials using the partial fraction expansion (34). From this calculation, we can see that the complex parameter dependence of the shape of P T (q,ω) [11][12][13][14][15][16][17] is explained from the behavior of the constituent peaks. [20].…”

“…This is achieved by replacing f (ω) and g(ω) by quadratic or higher order polynomials. The difference between the theory and the experiment in the quasielastic region of the spectrum of the polyisobutylene/decane solutions [16] may be explained by including the several relaxation times.…”

“…From these figures, we can distinguish three types of surface waves: the capillary wave mode, the elastic wave mode, and the viscoelastic relaxation mode, whose existence was pointed out in past articles [11][12][13][14][15][16][17]. As an example, we study the case ofσ = 10.0 shown in Fig.…”

“…They also examined the shape of the SDLS spectrum in detail by changing the liquid parameters [13]. Experimentally, the crossover between the capillary wave and the elastic wave is observed by the SDLS method [14][15][16], and the coexistence of these two modes is confirmed by using the excited surface wave method [17]. However, the reason why the peaks split in some cases and do not in other cases remains unclear.…”