A light-scattering study of 1-4 cis-trans polybutadiene

Authors:

• A. Aouadi,
• M.J. Lebon,
• C. Dreyfus,
• B. Strube,
• W. Steffen,
• Adam Patkowski,
• R.M. Pick

Abstract

Light-scattering measurements on 1-4 polybutadiene of two molecular weights have been carried out using two different tandem Fabry-Pérot interferometers in the back-scattering and 90° scattering geometries. The Rayleigh-Brillouin spectrum has been measured at different temperatures through the glass transition. Relaxation times and sound velocities have been fitted to a hydrodynamic formula, with as few independent parameters as possible. Comparison with previous measurements shows that the Brillouin relaxation times do not follow the structural or α relaxation. Forcing the fit either with the times of the α process or with a high-frequency relaxation channel does not yield satisfactory results. The only processes arising on a similar timescale and with comparable activation energies are intra-chain conformational changes rates as computed by molecular dynamics. A possible mechanism linking these conformational changes to the damping of the Brillouin lines is suggested.