Heterogeneity neutron scattering data

In this section we review recent investigations of dynamical heterogeneity of glass-forming polymers below and above Tg in terms of non-Gaussian parameter evaluated from incoherent neutron scattering data [ 139,140]. 

We may stress here that neutron scattering, like the X-ray scattering technique, cannot be considered as a direct means of measuring object dimensions. It only provides information on the spatial distribution of scattering heterogeneities or density fluctuations in the sample. Mathematical transformation of these data into information on the size of the heterogeneities is always based on certain model assumptions, the vahdity of which for real polymers still has to be proven. 

Data analysis of small angle-scattering X-ray and neutron data enables one to obtain information on particle shape, packing density, and heterogeneities. The reader is encouraged to refer to other references on this topic, as this is outside the scope of this paper. 

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