Supermolecular Liquid Crystals - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 56

assemblyproperties,whileatthesametimeretainingthefunctionalityofthe
supermolecule. These are properties not unlike those of a protein.
In the examples given in Fig. 64, the mesomorphic groups used for the
self-organization process are cyanobiphenyls. As with many of the other ex-
amples used previously in this article, lateral substitution of the mesogens
can be used to control the self-organization process to yield nematic phases.
The fist example given is for supermolecular material 57 , as shown in Fig. 65.
Although this material demonstrates that liquid crystal properties can be ob-
tained when a dendron is attached to a fullerene unit which is exposed on one
side of the resulting supermolecule, it nevertheless does not exhibit a nematic
phase, but instead an hitherto unidentified more ordered phase.
TheexposureofthefullereneunitisshowninFig.66.Themesogenic
groups cluster together as they stabilize an ensemble that would support the
formation of a liquid crystal phase. The exposed fullerene is then free to in-
teract with other fullerenes, thereby potentially stabilizing the formation of
a lamellar phase.
Nematic phases can be induced to form, however, by bifurcation at the sur-
face of the fullerene unit and the incorporation of mesogens that are laterally
attached. For example fullerene multipede 58 , see Fig. 67, shows an enan-
tiotropic chiral nematic phase, with a phase sequence of g 26 N ∗ 69 ◦ CIsoLiq,
which is useful for applications. The values of the pitch of the helix of the chi-
ral nematic phase obtained indicate that C 60 fits within the helical structure
formed by the mesogens themselves without causing any significant pertur-
bation of the pitch, see Fig. 68. This, in turn, implies that although the large
C 60 unit disturbs the mesogenic interactions, therefore lowering the clearing
point, it can be effectively camouflaged within the self-organizing chiral ne-
Fig. 66 Clustering of the mesogenic groups together in order to support the formation of
a lamellar phase, thereby leaving the fullerene unit exposed and free to interact with other
fullerene units