Dielectric anomalies in the β-relaxation of glassy 1,4-polybutadiene

We have measured the dielectric relaxation of the polymeric glass-former 1,4-polybutadiene in the glassy and supercooled liquid state. The loss spectra ϵ″ of the β-relaxation are measured between the lower detection limit at T = 125 K and T = 225 K > T_β, with T_β ≈ 210 K being the α-β-merging temperature. The related storage data ϵ′(ω) indicates that the β-process is a signature of supressing the higher frequency polarization with increasing temperature, rather than giving rise to additional polarizability at frequencies below the average relaxation frequency of the β-process. This observation, as confirmed by data obtained for o-terphenyl and salol, contradicts the previous understandings of the mechanism underlying the Johari—Goldstein-type β-process in glasses. A tentative link between the β-process and high frequency vibrational modes is established.