Dendron-stabilized liquid crystalline blue phases with an enlarged controllable range of the photonic band for tunable photonic devices

Liquid crystalline blue phases (BPs) show excellent potential for application in tunable photonic devices because they possess the unique optical property that the selective 3D Bragg diffraction in a visible wavelength region can be continuously shifted using an electric field. A new approach to simultaneously extend the wavelength range of field-induced Bragg diffraction shift and the temperature range of thermodynamically stable BPs is critically needed. Here, a new BP material system is shown using a dendron molecule to extend simultaneously the two BP ranges. One is the temperature range of thermodynamically stable BPs, which is expanded from 2.1 to 4.6 °C. The other is the reversible maximum shift range of Bragg wavelength on the electric field, which is extended from 85 to 109 nm. The physical mechanism of the dendron-stabilizing effect in BPs is discussed in terms of elastic property and orientational order of liquid crystal molecules. Liquid crystalline blue phases have great potential for advanced applications in tunable photonic devices. A new material system is developed with a dendron molecule, simultaneously enabling both the enlargement of the temperature range of thermodynamically stable blue phases and the continuously reversible maximum shift range of Bragg reflection in a visible wavelength region under an electric field.