The structural relaxation of polybutylacrylate films deposited on Si substrates has been studied by means of the Brillouin light-scattering technique. Measurements have been taken in the temperature range between 170 and 460 K. The contemporary presence in the spectra of the peaks relative to the longitudinal acoustic and longitudinal guided modes enabled us to obtain the whole set of relaxation parameters from analysis of Brillouin spectra. An Arrhenius scaling law and a Kohlraush-Williams-Watt relaxation function with a constant stretching exponent ${\mathrm{\beta }}_{\mathit{k}}$=0.45 have shown to be appropriate for interpreting our experimental data.

• Received 29 January 1993

DOI:https://doi.org/10.1103/PhysRevB.47.15286