Polymer characterization - Small-angle neutron scattering

With a wavelength of around 1 nm (10 Å), small-angle neutron scattering is an excellent technique for determining the average structure (conformation) of polymers in different environments.

The parameters measured are molecular mass, radius of gyration, persistence length or, more completely, polymer shape, as determined by light scattering and, sometimes, small-angle X-ray scattering.

As neutron sources are scarce, although open to all, this technique is primarily reserved for experiments where it is indispensable. Experiments that use isotopic substitution as a labeling method are therefore preferred. For example, determining the conformation of a polymer in its solid using deuterated chains is a unique possibility. Another possibility is the contrast variation method for obtaining partial structure factors of complex solutions, by varying the diffusing power of the solvent. It is applied to the determination of the structure of a graft polymer interface.