Supermolecular Liquid Crystals - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 43

by forcing the mesogens to pack closely together around the dendritic core.
The structures of the “hexagonal tubular nematic-columnar” and “rectan-
gular tubular nematic-columnar” phases are shown schematically together
in Fig. 51.
The hybrid structures of such “tubular nematic-columnar liquid crystal
phases” lend themselves as potential model systems for the development
of photonic band-gap materials, where large difference in refractive indices
between the inorganic and organic sections can be engineered into the sys-
tem through design and synthesis. In addition, the chiral nematic phase
of the hexadecamer shows the selective reflection of blue light indicating
that the pitch of the chiral nematic phase is sub-micron, approximately 0.2
to 0.3 m.

By swapping the position of the chiral group of the mesogen with the link-
ing group to the central scaffold, polypede 44 , see Fig. 52, is created where
the mesogens are attached end-on. As predicted, the material does not exhibit
columnar phases, but instead reverts to calamitic phases, with chiral nematic
and chiral smectic C ∗ phases being found. In terms of material properties,
the nematic phase of the supermolecule possesses a helical macrostructure
and therefore reflects light. The chiral smectic C ∗ phase is ferroelectric as
was shown by electrical field studies, however, the polarization was not deter-
mined because of the slowness of the response of the material.

µ

Fig. 52 Hexadecamer supermolecule 44