Quantifying Ion Distribution Profiles in Block Copolymers via Resonant Soft X-ray Scattering

Ion-doped block copolymers (BCPs) are a versatile, easy-to-process, and inexpensive class of materials with highly tunable structures. These attributes are promising for various applications, including nanolithography and ion/electron transport. The distribution of ions throughout a BCP phase is important to characterize, as it will affect the local polymer conformations, polymer/ion dynamics, and material performance. In this work, ionic liquid (IL) distributions in PS-b-PMMA were studied using resonant soft X-ray scattering (RSoXS). RSoXS harnesses the energy-dependent absorption of soft X-rays by organic functional groups to enhance chemical contrast in thin films, enabling interrogation of multicomponent systems without labeling. The ion distributions were spatially resolved via a data fusion approach, in which scattering patterns were generated from a newly developed simulation framework (https://github.com/usnistgov/NRSS) using real-space composition models mapped onto microscope images of the sample. Preliminary analyses suggested that the IL becomes more enriched near the center of the PMMA phase as total IL loading in the BCP is increased. These results provided a quantitative means to link the physics to material performance.