Dresden 2011 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 43: Soft Matter
DY 43.4: Vortrag
Freitag, 18. März 2011, 11:00–11:15, ZEU 118
Switching A Gelified Liquid Crystal — •Thomas Müller1, Maxim Khazimullin2, Ingo Rehberg1, Wolfgang Schöpf1, Alexei Krekhov3, Robin Pettau4, and Klaus Kreger4 — 1Experimental Physics V, University of Bayreuth, 95440 Bayreuth, Germany — 2Institute of Molecule and Crystal Physics, Russian Academy of Science, Ufa, Russia — 3Theoretical Physics I, University of Bayreuth, 95440 Bayreuth, Germany — 4Macromolecular Chemistry I, University of Bayreuth, 95440 Bayreuth, Germany
Liquid crystal displays make use of the electrooptical effect, caused by the orientation of the liquid crystals in an external electrical field above a certain threshold voltage (Fréedericksz effect). We investigate this effect in a new class of liquid crystal material, namely a diluted solution of an ABA-triblock copolymer in the nematic liquid crystal 5CB. The motivation of our studies is to obtain the physical parameters of this novel material with special emphasis on its dynamical behavior. In our experiments we use polarizing microscopy to detect the electrically controlled birefringence in homogeneous cells. We measure the temporal evolution of the light intensity when switching the electrical field above and below the threshold. It provides information about relaxation times of the director orientation, which can be used to determine the Fréedericksz threshold voltage and the elasticity of the gelified liquid crystal. Moreover, the relaxation times yield the rotational viscosity which contains information about the interaction between polymer molecules and liquid crystals.