The dynamics of poly(n-butyl acrylate) above the glass transition

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Abstract
Measurements of the dielectric constant of poly(n-butyl acrylate) have been taken in the frequency range 100 Hz-3 GHz, for temperatures between 254 and 359 K. Analysis of dielectric data and their comparison with results recently obtained on the same system by Brillouin light scattering have evidenced a two-step relaxation process. Dielectric spectra account for the behaviour of the slower process, i.e. the structural relaxation, while Brillouin spectra are particularly sensitive to the faster process, i.e. the secondary relaxation. The temperature behaviour of these processes is not in accordance with the predictions of the mode-coupling theory, while it can be suitably interpreted by a model that relates the high-frequency dependence of the dielectric loss curve to the local chain dynamics and the low-frequency dependence to the intermolecular correlation.