NON-LORENTZIAN RAYLEIGH SPECTRA OF BULK HOMOPOLYMERS FAR ABOVE THE GLASS-TRANSITION

Non-Lorentzian depolarized Rayleigh-scattering spectra have been clearly observed by Fabry-Perot interferometry in bulk homopolymers, polyisoprene and 1,4-polybutadiene, far above the glass-transition temperature. We have developed two alternative phenomenological methods for analyzing this kind of spectra. First of all we have used a scattering model function based on the Havriliak-Negami relaxation function which, in fact, is compatible with a Kohlrausch-Williams-Watts relaxation function in the time domain. In the case of polyisoprene, the results obtained by this method are in good agreement with the obtained ones through other different relaxation techniques when a similar method of analysis is applied. Besides, we have extended to the frequency domain the CONTIN algorithm which calculates an apparent distribution function of relaxation times from nonexponential time domain relaxation functions. The results obtained as well as the applicability of both methods are discussed.