![]() When synthesizing 2D polymers in single crystals, an external stimulus (most often light) converts a layered monomer crystal into a crystal composed of stacks of regularly covalently connected layers. This situation changes when reactions within single crystals are performed and SCXRD is used to analyse and monitor the process. The desired information is accessible despite crystal defects and crystal disorder. 1 As long as the diffractogram displays sufficiently sharp and assignable Bragg reflections, the quality of the crystals used for the analysis is of secondary importance. (5) To learn that strain management is mandatory for bringing about 2D polymerization and that detailed mechanistic understanding can provide valuable hints concerning polymerization strategy and monomer design.įor small-molecule synthetic chemistry single crystal X-ray diffraction (SCXRD) is an important analytical tool, for example, to confirm a particular atom–atom connection, determine bond lengths and angles or differentiate one stereoisomer from another. Comprehensive understanding thus requires knowing the time evolution of all components from monomer to product crystal (4) To understand that the mechanism of a 2D polymerization in a single crystal is in fact a complex 3D process that involves all components the crystal is composed of: monomers, templates, and solvents. (3) To learn that powder XRD, transmission electron microscopy (TEM) and electron diffraction are alternative methods to single crystal XRD for structural elucidation but that each of these methods has specific strengths and weaknesses which renders them comprehensive to one another rather than exchangeable. Local structural information is particularly important when monitoring the course of a chemical reaction within single crystals with XRD (2) To realize that Bragg XRD analysis provides information about the average structure of a single crystal, while the analysis of the diffuse scattering of the same crystal provides information about the local structure(s). Key learning points (1) To understand the structural insights and limitations which the analytical tool X-ray diffraction (XRD) offers His current research interests include structural changes in materials subjected to an external stimulus, which he pursues using experimental and computational methods. He came to ETH Zurich for his PhD where he investigated the growth mechanisms of 2D polymers using a wide range of X-ray diffraction methods. He studied earth sciences at the University of Vienna during which he specialised in crystalline phase-transitions under high pressures. Gregor Hofer is currently employed as a post-doc at the Materials Department of ETH Zürich. His research interest is the determination of real structures using diffuse X-ray scattering. Since 2016 he has been head of the X-ray platform at the Materials Department of ETH Zurich. After a three-year post-doctoral stay at the University of Berne, he moved to ETH Zurich in 2001, where he first worked as a senior scientist at the Laboratory for Crystallography. Thomas Weber studied mineralogy with focus on crystallography at the University of Munich (LMU), where he also received his PhD in 1998. Schlüter believes that organic chemistry is the fundament of polymer synthesis. His research interests are in the area of synthetic polymer chemistry. He studied chemistry and geophysics at the University of Munich (LMU) and worked at UC Berkeley, USA, University of Durham, UK (short term), MPI for Polymer Research, Mainz, Germany, Karlsruhe Institute of Technology, Karlsruhe, Germany, Free University of Berlin, Berlin, Germany and ETH Zürich, Switzerland. Dieter Schlüter is currently Professor Emeritus for polymer chemistry at the Materials Department of the ETH Zürich. This understanding will then be molded into a few guidelines that should help pave the way for future developments of 2D polymers by those interested in joining the effort with this fascinating and emerging class of 2D materials.Ī. Consequently, the reader will understand why some crystals break during polymerization, while others stay intact. The very heart of both techniques will be explained and it will be shown what can be safely concluded with their help and what not. The article will show that single crystal X-ray diffraction based on both Bragg and diffuse scattering are powerful techniques to achieve such goal. This raises questions as to how to elucidate the mechanism of these unusual polymerizations as well as their entire strain management. To have such an action proceed successfully, billions of bond formation processes have to be mastered exclusively in two dimensions within 3D crystals. Covalent long-range ordered (crystalline) sheets called 2D polymers have recently been synthesized by irradiating single crystals of suitably packed monomers.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |