Rotational friction at the molecular level
B. Jérôme; P. C. Schuddeboom; R. Meister; B. Jérôme; Department of Chemical Engineering, University of Amsterdam Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, and FOM-Institute for Atomic and Molecular Physics Kruislaan 407, 1098 SJ Amsterdam, The Netherlands; P. C. Schuddeboom; Department of Chemical Engineering, University of Amsterdam Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, and FOM-Institute for Atomic and Molecular Physics Kruislaan 407, 1098 SJ Amsterdam, The Netherlands; R. Meister; Department of Chemical Engineering, University of Amsterdam Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, and FOM-Institute for Atomic and Molecular Physics Kruislaan 407, 1098 SJ Amsterdam, The Netherlands
Журнал:
EPL (Europhysics Letters)
Дата:
2002-02-01
Аннотация:
We use second-harmonic generation measurements to follow the reorientation of liquid-crystal molecules in the first few molecular layers in contact with a surface. These measurements reveal four molecular relaxation times differing by orders of magnitude arising from different dissipation processes taking place at the interface with a solid. The slowest processes are due to the direct interaction of molecules with the solid, while the others concern molecules located just above this surface layer. This position-dependent dynamics explains some of the discrepancies previously observed in measurements of the surface reorientation dynamics of liquid crystals.
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