Neutron reflection to probe surface and interface segregation of polymers

Neutron reflectivity has been used to study the surface and interface segregation profiles of model polymer blends, consisting of deuterated and protonated polymers of high molecular weight. In this paper the authors discuss the factors involved in achieving an optimum experimental design, including the choice of substrate material and the label for the segregating species. The authors have found that neutron reflection is most useful when combined with a lower resolution, but direct, depth profiling technique, such as forward recoil spectrometry (FRES) or secondary ion mass spectrometry (SIMS). The direct profiling technique may be used to give a rough model of the profile, including integral measures of the segregation which constrain the possible profiles. A constrained profile can then be refined using the neutron reflectivity data. They discuss the principles of their experimental design and illustrate these with examples from their recent experiments