[Soft Matter Café] Off-specular neutron reflectometry for the investigation of polymer interfaces.

I will show the power of the off-specular scattering (OSS) technique combined with specular reflection (SR) to probe the properties of buried interfaces between immiscible polymer layers. The combined SR and OSS data analysis, obtained using a quick and robust originally developed algorithm, includes a common absolute scale normalization of both types of scattering, which are intricately linked, constraining the model to a high degree. This, particularly, makes it possible to readily distinguish between different instability scenarios of the interfaces and layers driven by either the nucleation and growth of defects (holes, protrusions, etc.), or by thermal fluctuations of the buried polymer/polymer interface. Finally, the 2D OSS maps will be exposed in different representations allowing to highlight particular features on the OSS maps. The use of those representations pave the way for qualitative interpretation of OSS data and to formulate a realistic model for the in-plane structure including long-range order, correlated roughness, bulk defects etc., by a simple eye inspection of different OSS maps prior to their quantitative refinement.

About the speaker:  After graduating in physics at Technical University Darmstadt, Philip Gutfreund obtained his PhD from Ruhr-University Bochum working on solid-liquid interfaces under shear, mainly using neutron reflectometry at the ILL. Since 2011 he is instrument scientist at the ILL, currently responsible for the FIGARO reflectometer. His main research interest is devoted to the microscopic structure and dynamics of polymeric liquids in out-of-equilibrium or in confinement, mainly using Neutron Scattering techniques. He also works on the development of the reflectometry technique per se, notably off-specular and grazing incidence scattering.