Dresden 2014 – scientific programme
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O: Fachverband Oberflächenphysik
O 101: Molecular Films: Electronics, Photovoltaics and Structure
O 101.6: Talk
Friday, April 4, 2014, 11:45–12:00, WIL A317
Structurally and kinetically controlled on-surface polymerization — •Johanna Eichhorn1, Wolfgang M. Heckl1, 2, and Markus Lackinger1, 2 — 1Physik-Department & TUM School of Education, Technische Universität München, 80799 München, Germany — 2Deutsches Museum, 80538 München, Germany
On-surface polymerization of functionalized building blocks is an established route to synthesize defined, periodic, covalently linked nanostructures. The arrangement of reactive side groups defines the network topology. The usage of different functional groups with different binding energies facilitates a controlled sequential coupling. Here, we present a hierarchical polymerization based on Ullmann-coupling by sequential dehalogention using bromine and iodine as leaving groups.
Room temperature deposition of 1-(4'-iodophenyl)-3,5-bis(4'-bromophenyl)benzene on Au(111) exclusively activates the iodine-phenyl bond dissociation, whereas the bromine-phenyl bonds remain stable. Subsequent dimerization yields new dumbbell shaped building block which self-assemble into large, periodic islands. Thermal annealing up to 375°C was used to also activate homolysis of the bromine substituents and initiate subsequent polymerization into covalent reticular networks. To compare the polymerization of building blocks with different bond topology, we also studied the direct polymerization of the monomer by deposition onto a preheated substrate. For both protocols the influence on the network quality of different kinetic reaction parameters was studied.