Liquid crystal ‘blue phases’ are highly fluid self-assembled three-dimensional cubic defect structures that exist over narrow temperature ranges in highly chiral liquid crystals1. The characteristic period of these defects is of the order of the wavelength of visible light, and they give rise to vivid specular reflections2 that are controllable with external fields3,4,5,6,7,8. Blue phases may be considered as examples of tuneable photonic crystals9 with many potential applications. The disadvantage of these materials, as predicted theoretically and proved experimentally1, is that they have limited thermal stability: they exist over a small temperature range (0.5–2 °C) between isotropic and chiral nematic (N*) thermotropic phases, which limits their practical applicability. Here we report a generic family of liquid crystals that demonstrate an unusually broad body-centred cubic phase (BP I*) from 60 °C down to 16 °C. We prove this with optical texture analysis, selective reflection spectroscopy, Kössel diagrams and differential scanning calorimetry, and show, using a simple polarizer-free electro-optic cell, that the reflected colour is switched reversibly in applied electric fields over a wide colour range in typically 10 ms. We propose that the unusual behaviour of these blue phase materials is due to their dimeric molecular structure and their very high flexoelectric coefficients. This in turn sets out new theoretical challenges and potentially opens up new photonic applications.
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Crooker, P. P. in Chirality in Liquid Crystals (eds Kitzerow, H.-S. & Bahr, C.) 186–222 (Springer, New York, 2001)
Stegemeyer, H. et al. Thermodynamic, structural and morphological studies on liquid-crystalline blue phases. Liq. Cryst. 1, 3–28 (1986)
Gleeson, H. F., Simon, R. & Coles, H. J. Electric field effects and two frequency colour switching in the cholesteric and blue phases of nematic/cholesteric mixtures (Tenth Int. Liquid Crystal Conf. (York, UK, July 1984; Paper G17). Mol. Cryst. Liq. Cryst. 129, 37–52 (1985)
Gerber, P. R. Electro-optical effects of a small pitch blue phase system. Mol. Cryst. Liq. Cryst. 116, 197–206 (1985)
Coles, H. J. & Gleeson, H. F. Electric field induced phase transitions and colour switching in the blue phases of chiral nematic liquid crystals. Mol. Cryst. Liq. Cryst. 167, 213–225 (1989)
Dmitrienko, V. E. Electro-optic effects in blue phases. Liq. Cryst. 5, 847–851 (1989)
Kitzerow, H.-S. The effect of electric fields on blue phases. Mol. Cryst. Liq. Cryst. 202, 51–83 (1991)
Heppke, G., Jerome, B., Kitzerow, H.-S. & Pieranski, P. Electrostriction of the cholesteric blue phases BP I BP II in mixtures with positive dielectric anisotropy. J. Phys. 50, 2291–2298 (1991)
Etchegoin, P. Blue phases of cholesteric liquid crystals as thermotropic photonic crystals. Phys. Rev. E 62, 1435–1437 (2000)
Cao, W., Muñoz, A., Palffy-Muhoray, P. & Taheri, B. Lasing in a three-dimensional photonic crystal of the liquid crystal blue phase II. Nature Mater. 1, 111–113 (2002)
Kitzerow, H.-S. et al. Observation of blue phases in chiral networks. Liq. Cryst. 14, 911–916 (1993)
Bohley, C. & Schart, T. Blue phases as photonic crystals. Proc. SPIE 5184, 202–208 (2003)
Kikuchi, H., Yokota, M., Hisakado, Y., Yang, H. & Kajiyama, T. Polymer-stabilized liquid crystal blue phases. Nature Mater. 1, 64–69 (2002)
Hisakado, Y., Kikuchi, H., Nagamura, T. & Kajiyama, T. Large electro-optic Kerr effect in polymer stabilised liquid-crystalline blue phases. Adv. Mater. 17, 96–98 (2005)
Parry, O., Nolan, P., Farrand, L. & May, A. L. Chiral dopants. UK Patent GB2329636 (31 March 1999).
Pieranski, P. in Chirality in Liquid Crystals (eds Kitzerow, H.-S. & Bahr, C.) 28–66 (Springer, New York, 2001)
Coles, H. J., Coles, M. J., Perkins, S. P., Musgrave, B. M. & Coates, D. Bimesogenic compounds and their use in flexoelectric liquid crystal devices. UK Patent GB2356629. (30 May 2001).
Patel, J. S. & Meyer, R. B. Flexoelectric electro-optics of a cholesteric liquid crystal. Phys. Rev. Lett. 58, 1538–1540 (1987)
Coles, H. J., Clarke, M. J., Morris, S. M., Broughton, B. J. & Blatch, A. E. Strong flexoelectric behaviour in bimesogenic liquid crystals. J. Appl. Phys. (submitted)
Wu, S. T. & Yang, D.-K. Reflective Liquid Crystal Displays Ch. 1 (Wiley, Chichester, UK, 2002)
H.J.C. thanks the EPSRC, UK, who funded the materials research under their Displays and Functional Materials initiatives. Author Contributions H.J.C. invented the flexoelectric materials, was responsible for the project planning, wrote the Letter and was responsible for the tentative explanation. M.N.P. carried out all the experimental work, including microscopic texture and data analysis.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
About this article
Cite this article
Coles, H., Pivnenko, M. Liquid crystal ‘blue phases’ with a wide temperature range. Nature 436, 997–1000 (2005). https://doi.org/10.1038/nature03932
Thermal stability and electro-optical characteristics of polymer stabilised blue phase liquid crystalline materials: a role of polymer concentration
Liquid Crystals (2020)
An Overview of Liquid Crystal Techniques and Technology with Applications to Different Research Fields
Defect and Diffusion Forum (2020)
International Journal of Thermophysics (2020)
Journal of Optics (2020)