Liquid Crystalline Blue Phases - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 102

AsearchoftheWebofScienceusing“bluephase”or“bluephases”asakey-
word reveals a rapid expansion in the number of studies since then, from only
seven in the 1970s to 174 in the 1980s and 232 in the 1990s.
4
Simple and Double Twists
The results of experiments examining light diffraction proved that blue
phases form huge cubic crystals with a lattice parameter approximately
equivalent to the wavelengths of light (around a few hundred nanometers).
This means that a single unit lattice contains as many as 10 7 molecules. The
toughest challenge the researchers of blue phases faced was identifying the
structural arrangement of this many molecules within such a lattice. The
basic form of this arrangement is a “twist”.
Let us consider molecular arrangements based on the twist. As shown in
Fig. 1, a chiral nematic phase consists of a helical structure of molecular ar-
rangements. Such a structure is commonly found in nature and is one of
the typical self-assembled molecular arrangements. Generally, a liquid crystal
phase with a helical structure either consists of or contains chiral molecules.
Due to the intermolecular interaction among the chiral molecules, the rod-
shaped liquid crystal molecules become more stable when their long axes are
slightly twisted together, rather than aligned in parallel. It is understood that
the liquid crystal molecules form a helix, since the sense of the twist is the
same for all molecules. In this case, the twisted molecular structure is formed
along a single axis in the lateral molecular direction (perpendicular to the
long axis), and is known as a “simple twist”. Each molecule rotates rapidly
Fig. 1 Helical arrangements of molecules in a chiral nematic phase