Liquid crystal ‘blue phases’ with a wide temperature range

摘要: Liquid crystal 'blue phases' are highly fluid self-assembled three-dimensional cubic defect structures that exist over narrow temperature ranges in chiral liquid crystals. The characteristic period of these defects is the order wavelength visible light, and they give rise to vivid specular reflections controllable with external fields. Blue phases may be considered as examples tuneable photonic crystals many potential applications. disadvantage materials, predicted theoretically proved experimentally, have limited thermal stability: a small range (0.5-2 degrees C) between isotropic nematic (N*) thermotropic phases, which limits their practical applicability. Here we report generic family demonstrate an unusually broad body-centred phase (BP I*) from 60 C down 16 C. We prove this optical texture analysis, selective reflection spectroscopy, Kossel diagrams differential scanning calorimetry, show, using simple polarizer-free electro-optic cell, reflected colour switched reversibly applied electric fields wide typically 10 ms. propose unusual behaviour blue materials due dimeric molecular structure very high flexoelectric coefficients. This turn sets out new theoretical challenges potentially opens up