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PO: Polymerphysik
PO 12: Poster: Flüssigkristalline Polymere
PO 12.6: Poster
Tuesday, March 2, 1999, 14:00–16:00, Foyer
Molecular Orientation and Dynamics in Ferroelectric Diblock Copolymers monitored by FT-IR Spectroscopy — •M. Abdallah1, S. V. Shilov2, F. Kremer1, G. Mao3, Ch. Ober3, and M. Brehmer4 — 1Department of Physics, University of Leipzig, Linnéstr. 5, 04103 Leipzig, Germany — 2Institute of Macromolecular Compounds, Bolshoi pr. 31, 199004, St. Petersburg, Russia — 3Department of Materials Science and Engineering Cornell University, Ithaca NY, 14853 USA — 4Bergische Universität Wuppertal, 42097 Wuppertal, Germany
In ferroelectric liquid crystalline block copolymers the properties of
ferroelectric liquid crystals (LC) are combined with those of diblock
copolymers: hence one observes in these materials a microphase separation
between the amorphous polymer (polystyrene [PS]) and the ferroelectric
liquid crystal segment. The latter group can be switched by applying an
external electric field ( <104 V cm−1). FT-IR spectroscopy
(time-resolved) was employed to study structure and dynamics in these
systems. From analysis of the dichroism of the FT-IR spectra, it was
concluded that the components in the PS microphase are oriented randomly
while the liquid crystalline groups form an ordered phase. Time-resolved
measurements of the switching of the LC block were performed during the
application of an external electric field. It may be shown that switching is
of an electroclinic type and that the tilt angle and the mesogenic motion
increases with temperature especially if the PS block is heated above Tg.
The orientation of the LC block after heating to the isotropic phase is
completely restored due to the memory effect of the polymer
microstructure.
Merenga, A.S.; Kremer, F.; Ober, C.; Mao, G.; Brehmer,
M. in
press Macromolecules 1998