Orientation and conformation in nanoscale amorphous regions often dominates the properties of soft materials such as composites and semicrystalline polymers. Robust correlations between structure in these amorphous regions and important bulk or thin film properties are not well developed due to a lack of measurements with high spatial resolution and a sensitivity to molecular orientation. I will describe our approach to solving this issue using polarized resonant soft X-ray scattering (P-RSoXS), which combines principles of soft X-ray spectroscopy, small-angle scattering, real-space imaging, and molecular simulation to produce a molecular scale structure measurement for soft materials and complex fluids.<br/><br/>Because P-RSoXS is new to the soft material community, I will first cover the basics of the measurement. The fundamental principles of P-RSoXS and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, the spectroscopic basis for P-RSoXS, will be reviewed. The P-RSoXS experiment will be discussed including sample preparation and constraints, which differ considerably from analogous scattering techniques such as conventional small-angle X-ray scattering (SAXS) and small angle neutron scattering (SANS). I will also cover approaches for including gases or liquids in the experiment, and describe available measurement facilities. Data collection best practices will be reviewed.<br/><br/>I will then describe polarized resonant soft X-ray scattering (P-RSoXS) measurements of several model systems including nanocomposites and semicrystalline polymers. Analysis will focus on quantitative extraction of orientation details from nanoscale glassy regions. This work is now accelerated by a powerful analysis framework using parallel computation across graphics processing units (GPUs) for the forward-simulation of P-RSoXS patterns. Certain model systems have been amenable to quantitative fitting of orientation parameters using this approach. I will conclude with a discussion of the broad prospects for P- RSoXS measurements informing and guiding the processing and synthetic design of soft materials.

Polarized resonant soft X-ray scattering measurements in glasses and semicrystalline polymers

ACS Spring Meeting 2021

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