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.