title: Decorating the Edges of a 2D Polymer with a Fluorescence Label.
abstract: This work proves the existence and chemical addressability of defined edge groups of a 2D polymer. Pseudohexagonally prismatic single crystals consisting of layered stacks of a 2D polymer are used. They should expose anthracene-based edge groups at the six (100) but not at the two pseudohexagonal (001) and (001̅) faces. The crystals are reacted with the isotopically enriched dienophiles maleic anhydride and a C18-alkyl chain-modified maleimide. In both cases the corresponding Diels-Alder adducts between these reagents and the edge groups are formed as confirmed by solid state NMR spectroscopy. The same applies to a maleimide derivative carrying a BODIPY dye which was chosen for its fluorescence to be out of the range of the self-fluorescence of the 2D polymer crystals stemming from contained template molecules. If the crystals are excited at λ = 633 nm, their (100) faces and thus their rims fluoresce brightly, while the pseudohexagonal faces remain silent. This is visible when the crystals lie on a pseudohexagonal face. Lambda-mode laser scanning microscopy confirms this fluorescence to originate from the BODIPY dye. Micromechanical exfoliation of the dye-modified crystals results in thinner sheet packages which still exhibit BODIPY fluorescence right at the rim of these packages. This work establishes the chemical nature of the edge groups of a 2D polymer and is also the first implementation of an edge group modification similar to end group modifications of linear polymers.
authors.affiliation: Institute of Polymers, Department of Materials, Swiss Federal Institute of Technology, ETH Zürich , Vladimir Prelog-Weg 5, 8093 Zürich, Switzerland.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Institute of Polymers, Department of Materials, Swiss Federal Institute of Technology, ETH Zürich , Vladimir Prelog-Weg 5, 8093 Zürich, Switzerland.
authors.forename: Richard H M
authors.initials: RH
authors.lastname: Bernitzky
authors.affiliation: Institute of Polymers, Department of Materials, Swiss Federal Institute of Technology, ETH Zürich , Vladimir Prelog-Weg 5, 8093 Zürich, Switzerland.
authors.forename: Max J
authors.initials: MJ
authors.lastname: Kory
authors.affiliation: Institute of Polymers, Department of Materials, Swiss Federal Institute of Technology, ETH Zürich , Vladimir Prelog-Weg 5, 8093 Zürich, Switzerland.
authors.forename: Gregor
authors.initials: G
authors.lastname: Hofer
authors.affiliation: Divison of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven , Celestijnenlaan 200 F, 3001 Heverlee, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Hofkens
authors.affiliation: Institute of Polymers, Department of Materials, Swiss Federal Institute of Technology, ETH Zürich , Vladimir Prelog-Weg 5, 8093 Zürich, Switzerland.
authors.forename: A Dieter
authors.initials: AD
authors.lastname: Schlüter