Polarized Resonant Soft X-Ray Scattering to Characterize Conformations of Polymer Chains Grafted to Nanoparticles

Polymer-grafted nanoparticles are of considerable interest across various industrial and scientific fields, particularly in the development of advanced nanomaterials with tunable properties, nanocomposites, and drug delivery systems. This study utilized polarized resonant soft X-ray scattering (P-RSoXS) to analyze the spatially resolved molecular orientation of polymer chains grafted onto surfaces. The samples investigated consisted of monolayer thin films of polystyrene-grafted gold and iron oxide nanoparticles of different shapes and sizes. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were performed to characterize the shape and size of the nanoparticles. P-RSoXS measurements were carried out across the carbon K-edge to assess chain orientation using the 1s→π* transitions of the pendant phenyl group of polystyrene. This revealed scattering anisotropy, which is indicative of polymer chain orientation. To quantify the extent of polymer chain orientation close to the particle surfaces, scattering simulations were performed (https://github.com/usnistgov/NRSS). The present study elucidates how the orientations of grafted polymer chains are influenced by the shape of nanoparticles, specifically in the case of spherical and cubic geometries. Additionally, this research demonstrates that P-RSoXS is an effective technique for quantifying nanoscale chain stretching in polymer nanocomposites, even at lower levels of detection.