STUDY OF THE STRUCTURAL RELAXATION OF POLYACRYLATES BY BRILLOUIN LIGHT SPECTROSCOPY

The structural relaxation of glass-forming polyacrylates has been stud ied by means of the Brillouin light scattering (BS) technique in the f requency range between 1 and 30 GHz. The specimens, consisting of tran sparent polyacrylate films supported by an opaque substrate, were anal yzed by means of a high-contrast and high-resolution Fabry-Perot tande m interferometer. The entire set of relaxation parameters were obtaine d by the full spectrum analysis of BS data, at different temperatures. Analysis of BS measurements and their comparison with dielectric data taken on the same systems show that BS is sensitive to the alpha + be ta relaxation at the highest temperatures and to the beta relaxation f or temperatures approaching the glass transition temperature, T-g.