Brillouin and Rayleigh scattering in polybutadiene

Abstract

Light scattering studies of polybutadiene from 110 to 350°K reported herein include measurements of Brillouin shift, Brillouin linewidth, and Rayleigh depolarization ratios as functions of temperature. The hypersonic attenuation coefficient over one wavelength (α λ_s) is insensitive to temperature variation below T_g; above T_g, α λ_s increases rapidly with increasing temperature. The sound attenuation theory of Woodruff and Eihsenreich gives an adequate description of the measure α λ_s value below T_g; no quantitative theory describes the sound attenuation above T_g. The Krishnan effect, depolarization ratio ρ_n = V_h/H_n ≠ 1, was observed for polybutadiene below 250 °K. The frozen‐in density fluctuation mechanism proposed by Mueller fails to explain the effect; frozen‐in fluctuations of the dielectric anisotropy are a possible mechanism.