Optical retardation and structure of developable domains in tubular discotic liquid crystals

The simplest distorted texture of tubular discotic materials are “developable domains”. For small curvature, the tubes are expected to bend circularly around a straight line core. We have observed the birefringence fringes from such a texture in the hexapentoxytriphenylene, close to the isotropic transition. The optical retardation shows a cusp-like singularity above the core. It can be quantitatively described by the assumed circular texture for the tubes. The birefringence is Δn = 0.14 ± 0.01 for λ = 0.65 μm.