Dresden 2020 – scientific programme
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O: Fachverband Oberflächenphysik
O 63: Focus Session: Functional Molecules at Surfaces III
O 63.9: Talk
Wednesday, March 18, 2020, 12:45–13:00, TRE Ma
Bending and twisting of C-C bonds by mechanical lifting of surface-adsorbed polymers — •Philipp D'Astolfo1, Guilherme de Vilhena1, Carl Drechsel1, Xunshan Liu2, Silvio Decurtins2, Shi-Xia Liu2, Rémy Pawlak1, and Ernst Meyer1 — 1Department of Physics, University of Basel, Basel, Switzerland — 2Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
The torsion and rotation about single carbon-carbon bonds is a natural process that is ever-present in Chemistry- and Surface-Sciences. Due to their small magnitude, measurements of force-induced conformational changes between units of a long polymeric chain have proven difficult until now[1]. To shed light on these processes, we performed lifting experiments using atomic force microscopy (AFM) at 4.8K of different cyclic carbon polymers adsorbed on a gold substrate. In the pulling curves we detected alternating periods related to successive unit detachments of the poly-pyrenylene units vertically lifted from the Au(111) surface. Molecular dynamic (MD) simulations attribute those spacing variations to symmetry-broken bent and rotated conformations of the sliding physisorbed segment and steric hindrance by the just lifted monomer[2]. In a second experiment, we pulled asymmetric cyclopentaaceanthrylene-polymers that revealed more complex detaching periods depending on the adsorption motif of the polymer units and the resulting steric hindrance between them.
[1] Kawai et al., PNAS, 2014, 11, 111, 3968-3972.
[2] Pawlak et al., Nano Lett., 2019 submitted.
[3] D'Astolfo et al., manuscript in preparation.