Supermolecular Liquid Crystals - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 23

then attached to pentaerythritol itself, via formation of the propanoic acid
derivative.
In the materials discussed in the next section, the mesogenic groups have
four aromatic rings, in order to promote mesomorphic behavior. In all of the
examples a chiral unit was included into the structure of the mesogens, and
in the first of the materials, dendrimer 31 , see Fig. 25, a chiral 2-methylbutyl
group was appended laterally to the long axes of the mesogens. As expected,
the terminally appended material exhibited a smectic phase, in this case chi-
ral smectic C ∗ , but in addition, a chiral nematic phase was also exhibited. The
local structure of the smectic C phase is shown in Fig. 26, where the mesogens
are constrained into a cylindrical conformation. The mesogens are located
towards the layer interfaces and the aliphatic spacers or linking groups are to-
wards the interiors of the layers. The mesogens are also tilted with respect to
the layer plains, but this does not indicate that the cylindrical structures are
tilted, rather just that the mesogens are at an angle to the layers. The material
Fig. 25 Dendrimer 31 with terminally appended mesogens which themselves have laterally
appended chiral groups