Sattela H, Loubiri I and Gharbia M
It’s well known that the optical retardation measurement depends directly on the birefringence of the liquid crystal. We are interested by the simplest distorted texture of discotic columnar liquid crystals (DCLC) where the columns curve circularly their structures around the core line. The present opportunity is to use a hexagonal columnar structure where the topology of columns hemispheres is well known. We have observed the DCLC interference fringes from a half drop in the hexa-n-hexyloxytriphenylene close to the isotropic transition. Using polychromatic spectral lamp, the optical retardation symmetry has been used to describe the spherical texture of the columns. The present work shows that the optical retardation exhibits a noticeable difference between the birefringence measurement Δn versus the wavelength λ. The birefringence is given by the relationship: , (Δno=-0,196 and B=0,023 μm2).
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