Surface modes on polymer solutions by surface light-scattering techniques

Abstract

By using the surface heterodyne spectroscopy, we study the surface modes on polymer solutions of polyisobutylene/decane at different concentrations. For each concentration, we measure the power spectra at various wave numbers (110.0–600.0 cm−1). We find that the relation between the frequency shift ωk of the power spectrum and wave number k changes continuously from ωk∝k3/2 to ωk∝k when concentration of the polymer solution is changed from 0.5 g/dl to 8.0 g/dl. For the low-concentration polymer solutions, the surface modes are capillary modes (ωk∝k3/2). For the high-concentration polymer solutions, the surface modes are elastic modes (ωk∝k). This result is compared with the theory [J. L. Harden, H. Pleiner, and P. A. Pincus, J. Chem. Phys. 94, 5208 (1991)].