Relaxation spectra in poly(methylmethacrylate): Comparison of acoustic attenuation and light scattering data

Relaxation processes in polymethylmethacrylate were investigated using ligh t scattering and mechanical relaxation techniques. The acoustic attenuation data cover the frequency range from 1 Hz to 17 GHz and the light scatterin g from 0.5 to 10 000 GHz. Analysis of the data in a broad temperature range (80-350 K) shows that the model of the asymmetric double-well potentials, traditionally used for description of the acoustic attenuation in glasses, cannot describe all the data consistently. It is shown that assuming an add itional relaxation in GHz region with a constant loss spectrum provides a g ood agreement of the model with experimental data. (C) 2001 American Instit ute of Physics.