It depends on the structure that you want to observe.
In SANS, hydrogen and deuterium yield contrast. Therefore, if you mix deuterium-replaced chains in a polymer sample, you can analyze the morphology of single chains.
Considering the accessibility to the Neutron facilities, however, X-ray scattering or microscopic methods may be more useful.
Neutron Scattering in general is a very good probe for polymer. As neutrons are neutral, the penetration is high, therefore with very low (thermal) energy neutrons, which does not damage the polymer, one can probe the bulk properties of polymer. SANS is one of the many techniques that uses neutron as probe. This is suitable to study the shape and size of dispersed colloidal (or nano) particles in a matrix (liquid or solid). I mainly work with surface and have experience of working with Neutron Reflectivity for polymer samples. You may see the following ref.