| Summary: | <p>Polymers and macromolecules are widely used in the medical and pharmaceutical fields due to their outstanding biocompatibility, low density, and relatively low cost. However, the lack of microstructural study on these materials limits the ability to tailor them for broader and deeper applications.</p>
<p>As important methods for microstructural research, electron microscopic techniques have the potential to image polymers and macromolecules, but these materials are challenging for conventional electron microscopies because of their low crystallinity, poor contrast and severe beam damage. Therefore, an electron microscopic technique that uses reduced dose and also has higher contrast from light elements is required for the microstructural study.</p>
<p>Electron ptychography is an electron efficient imaging mode that offers phase contrast for light element detection. After the acquisition, a 4D dataset comprising the intensity in the STEM detector plane recorded as a function of each probe position can be reconstructed to give a phase image. Hence, electron ptychography has lower sample damage and better phase contrast compared to traditional techniques, which is helpful to overcome the existing challenges.</p>
<p>In this work, electron ptychography has been applied to explore the fine structures, particularly how light atoms order, in polyvinyl alcohol (PVA, a polymer) and some peptide amphiphiles (macromolecules). In the future, it is expected that the methodology can be expanded to other polymeric and macromolecular systems, and thus, better microstructural understanding could contribute, for example, to better medical and pharmaceutical applications of polymers and macromolecules.</p>
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