Blue phases are types of liquid crystal phases that appear in a temperature range between a chiral nematic phase and an isotropic liquid phase. Because blue phases have a three-dimensional cubic structure with lattice periods of several hundred nanometres, they exhibit selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of applications, although blue phases are of interest for fast light modulators or tunable photonic crystals, the very narrow temperature range, usually less than a few kelvin, within which blue phases exist has always been a problem. Here we show the stabilization of blue phases over a temperature range of more than 60 K including room temperature (260–326 K). Furthermore, we demonstrate an electro-optical switching with a response time of the order of 10−4 s for the stabilized blue phases at room temperature.

Polymer-stabilized liquid crystal blue phases

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

Critical phenomena and renormalization-group theory

Supramolecular Chirality in Self-Assembled Systems

The potential of palladacycles: more than just precatalysts

We report the first observation of cholesteric blue phases in chiral anisotropic polymer networks. In two-component mixtures of a chiral and a non-chiral diacrylate, we observed typical textures of BPI, BPII and BPIII phases. By photopolymerization of these materials at constant temperature we obtained blue phase networks. After polymerization, the blue phases were stored, which enabled us to further study them without any temperature control.

Observation of blue phases in chiral networks

Assembling achiral molecules typically generates achiral domains. However, odd things can happen when the molecules are banana-or boomerang-shaped—their cores can twist out of plain to form left- or right-handed helices, which can then pack into chiral domains that will polarize light (see the Perspective by Amabilino ). Hough et al. (p. [452][1]) show that if you make the situation even more complex by frustrating the packing of adjacent layers, you can create a material that appears to be macroscopically isotropic with only very local positional and orientational ordering of the molecules but still shows an overall chirality. In a second paper, Hough et al. (p. [456][2]) also show that if you change the chemistry of the molecules to allow for better overall packing, you can create a situation where helical filaments form that also tend to pack in layered structures. However, the frustration between the two types of packing leads to macroscopically chiral and mesoporous structures.

 [1]: /lookup/volpage/325/452
 [2]: /lookup/volpage/325/456

https://science.sciencemag.org/content/sci/325/5939/456.full.pdf

Helical Nanofilament Phases

Liquid crystals are of major technological importance for display devices, as well as being of fundamental molecular interest Understanding how their building-block molecules arrange themselves is critical for obtaining improvements in performance In their research commentary, Heppke and Moro discuss recent findings about how the chirality, or handedness, of the underlying molecules influences the behavior of liquid crystals

Chiral Order from Achiral Molecules

The dynamics of different molecular modes in four antiferroelectric liquid crystal substances have been studied by a combination of spectroscopic methods. The fastest motion is the reorientation ar ...

Collective and non-collective excitations in antiferroelectric and ferrielectric liquid crystals studied by dielectric relaxation spectroscopy and electro-optic measurements

In this preliminary report we present the mesomorphic properties and electro-optic investigations of three new 'banana-shaped' mesogens. The materials are structurally similar to Niori's the original bent-core materials but possess alkylthio substituents in place of alkoxy substituents. Microscopic investigations revealed an unusual 'spiral-domain texture', similar to that observed in the 'B7' phase of related materials. Further investigations support our earlier observations that the materials display antiferroelectric switching in this phase, in two of the new materials studied. The nature of this phase, in comparison with the 'switchable' (B2) and 'chiral-domain' (B4) phases of the original materials, is discussed.

Gerd Heppke

Papers

Observation of blue phases in chiral networks

Helical Nanofilament Phases

Chiral Order from Achiral Molecules

Collective and non-collective excitations in antiferroelectric and ferrielectric liquid crystals studied by dielectric relaxation spectroscopy and electro-optic measurements

Novel sulphur-containing banana-shaped liquid crystal molecules