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Leipzig 1999 – scientific programme

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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. Brehmer41Department 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

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