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O: Fachverband Oberflächenphysik
O 7: Focus Session: Functional Molecules at Surfaces I
O 7.2: Vortrag
Montag, 16. März 2020, 10:45–11:00, TRE Ma
Giant thermal expansion triggered by alkyl chain functionalization — •Sebastian Scherb1, Antoine Hinaut1, Rémy Pawlak1, Guilherme Vilhena1, Sara Freund1, Zhao Liu1, Klaus Müllen2, Thilo Glatzel1, Akimitsu Narita2, and Ernst Meyer1 — 1Department of Physics, University of Basel, Basel, Switzerland — 2Max Planck Institute for Polymer Research, Mainz, Germany
Thermal expansion, the response in shape or size of a solid to heat, is a fundamental property governing their mechanical applicability. Due to various mechanisms involving intrinsic flexibility, conformational changes and weak intermolecular interactions, molecular architecture allows negative and large positive expansions [1]. However, understanding of the underlying mechanisms down to the molecular scale remains elusive.
Here, we investigate the influence of alkyl chain functionalization on the thermal response of molecular assemblies by non-contact AFM, STM and molecular dynamic simulations (MD) at different temperatures [2,3]. Upon heating from 5 K to 300 K the alkyl chains undergo large thermal fluctuations compared to the cores because of entropic effects and large anharmonic vibrations [3]. This results in temperature-dependent intermolecular interactions that promote a giant expansion of the networks with temperature.
[1] Liu, Z. et al. Chem. Commun. 54, 5164-5176 (2018).
[2] Hinaut et al., Nanoscale, 10, 1337-1344 (2018).
[3] Scherb, S. et al., in preparation (2019).