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The Experiment

First Results

Contrary to the molecules of classical fluids such as water, the long molecules of a liquid crystal can be oriented when subject to an external field. This property has lead in particular to the invention of the well-known screens for watches or computers. In this case, it is an electric field which forces the molecules to point in a particular direction, changing the polarity of the light passing through the liquid crystal layer. In our experiment, the external field applied to the liquid crystal layer is a shearing stress created by the rotation of one of the two glass plates between which is contained the layer. As seen on the following pictures, domains of differently oriented molecules are observed between crossed polarizers. At high shear, a complex state that we call "orientational turbulence" is observed. This turbulence has the amazing property to melt when the shear stress is reduced. Surprisingly, only domains having a double structure can survive, the single ones disappear. We think that these domains are each of them constituted of two differently oriented molecules. The theoretical understanding of these new findings is currently under progress.

 

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