Dynamics of Glass-Forming Polymers: “Homogeneous” versus “Heterogeneous” Scenario

The question of whether the primary $\alpha$ relaxation in glass-forming systems is homogeneous or heterogeneous in nature is investigated by incoherent neutron scattering techniques in glass-forming polymers. It is shown that the momentum transfer dependence of the Kohlrausch-Williams-Watts relaxation time allows one to discriminate between these two limiting scenarios. From the results obtained we can conclude that the apparent stretching of the $\alpha$-relaxation function relates dominantly to sublinear diffusion and is not a result of heterogeneities in the material.