Advances in ripplon surface laser-light scattering measurement for highly viscous polymer-solvent system

The surface properties of a polymer organic-solvent system was measured using a ripplon surface laser-light scattering (SLLS) technique. The power spectrum (PS) of a ripplon can be obtained by fast Fourier transform (FFT) analysis of the beat signal of scattered light using ripplon SLLS. However, the PS peak shifts to lower frequencies due to the low surface tension of typical organic solvents. This shift means that the PS can be easily affected by external vibrational noise. In addition, higher viscosities broaden the shape of the spectra so that the peak becomes less clear. It is therefore difficult to find a definite peak frequency and to determine its width at half maximum for analyzing surface properties. To address these issues, a new system for SLLS was developed and was used to demonstrate that the available viscosity measurement range can be extended to the higher values needed for organic-solvent systems.