Study of the Dynamic Structure Factor in theβRelaxation Regime of Polybutadiene

Using neutron spin echo and dielectric spectroscopy we have studied the molecular motions of 1-4 polybutadiene in the $\alpha -\beta$ relaxation regime. At the first peak of the static structure factor the relaxation times follow the temperature dependence of the viscosity, while near the second peak the Arrhenius law of the $\beta$ relaxation is observed. Considering localized motions on a length scale of 1.5 Å with the barrier distribution from dielectric spectroscopy the dynamic structure factor in the $\beta$ relaxation regime can be described quantitatively.