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Explore Synthesis and Structural Determination of Crystalline Supramolecular Polyaniline Thin-Films and 2D Polyanilines Assisted by Electron Diffraction and TEM Imaging

Subject Area Preparatory and Physical Chemistry of Polymers
Term from 2019 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 426572620
 
Final Report Year 2024

Final Report Abstract

The project was aimed at the development of a novel surfactant-monolayer-assisted interfacial synthesis (SMAIS) method towards highly crystalline supramolecular polymer and 2D covalent polyaniline (2DCP) thin films with large-sized crystalline domains and the development of suitable TEM techniques to fully disclose the crystalline structure of the synthesized materials. As a robust strategy, the SMAIS method has been employed to guide the preorganization and 2D polycondensation of rigid monomers on the water surface by taking advantage of the unique chemical reactivity and selectivity. This approach enables the synthesis of large-area (~50 cm2), highly crystalline quasi-2D polyaniline ultrathin films with tunable thicknesses from ~2.6 to ~30 nm. Using in situ surface-specific spectroscopy, we elucidated the molecular-level mechanism underlying the formation of the crystalline quasi-2D polyaniline film. Building upon this foundation, we extended the synthesis to other synthetic chemistry and have recently demonstrated the successful synthesis of highly crystalline 2D polyamide, 2D polyimide, 2D polyimine, 2D polyboronate ester, 2D poly(pyridinium salt) and 2D poly(vinylene). In order du disclose the structure of the layer stacked 2D organic materials we improved the low-dose technique through which we were able to obtain clear images of imine-linked 2DCPs and study the formation process of grain boundaries. Through the optimization of the acceleration voltage of the TEM we were further able to increase the resolution on imine-linked 2DCPs up to 1.9 Å. This allowed us to detect interstitial defects in the polymer layers for the first time. Through the thorough comparison of different metal-organic frameworks, with slightly altered structural features we identified and understood important aspects contributing to the stability of said materials. Through this we were able to push the obtained resolution from 2.5 Å down to 1.0 Å at 300 kV and even down to 0.9 Å at 80 kV. This resulted in a full disclosure of the investigated structure.

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