Orientation and conformation in nanoscale amorphous regions often dominates the properties of soft materials such as composites and semicrystalline polymers. In polyethylene (PE), interlamellar amorphous tie chains have been shown to substantially reduce the rate of slow crack growth, which is important for long service life in infrastructure elements such as potable water pipes. In this presentation I will describe our polarized resonant soft X-ray scattering (P-RSoXS) measurements of semicrystalline polyethylenes. The P-RSoXS of PE is highly anisotropic with respect to electric field vector and the orientation of the amorphous interlamellar chains is a significant contributor. I will discuss our development of real-space models from detailed low-angle annular dark field scanning transmission electron microscopy (LAADF-STEM), followed by the forward simulation of RSoXS patterns from these models. Our initial comparisons strongly suggest an interlamellar amorphous region that has an average molecular long axis orientation orthogonal to molecular long axes within the crystalline lamellae. Some possibilities for the origin of this orientation could be re-entrant chain region or the behavior of free amorphous chains in confinement. Real space models featuring this orthogonal component do reproduce, upon forward simulation, all salient features of the P-RSoXS pattern including trends in anisotropy with energy, trends in anisotropy with q, and a clear long period peak. Prospects for a general measurement framework using P-RSoXS with LAADF-STEM that is applicable to a wide variety of semicrystalline polymers and employs a flexible forward simulation approach will be discussed.

Semicrystalline polymer morphology from polarized resonant soft x-ray scattering

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.