Supermolecular Liquid Crystals - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 45

similar to that of material 45 . The clearing point is relatively high; however,
due to the inclusion of chiral groups, the glass transition is low. The wider
temperature range for liquid crystal properties to be observed, however, does
not reveal any other phases than smectic A.
2.7
Effect of Hard Core Scaffolds - Molecular “Boojums”
The incorporation of lateral mesogenic substituents onto a [60]fullero-scaffold,
particularly chiral mesogens, can lead to interesting structural behavior and
properties. For example, supermolecular material 47 , shown in Fig. 55, has
a structure that utilizes the same laterally appended mesogens as in material
43 shown in Fig. 46, but this time attached to a [60]fullerene (C 60 )centralcore
unit [98]. Through bifurcation, 12 mesogenic units were symmetrically po-
sitioned about the C 60 core, thereby creating a spherical architecture. Again,
because of the lateral attachment of the mesogenic units, a chiral nematic phase
is exhibited by this material. The material forms a glass at 47 ◦ C, and upon heat-
ing a chiral nematic phase is stable up to 103 ◦ C. Unlike compound 43 , however,
for 47 no columnar phases were observed, thereby strengthening the view that
[60]fullerene suppresses mesophase polymorphism.
The mesophase defect textures exhibited by 47 were typical of those nor-
mally found for a chiral nematic phase, except they were only revealed upon
annealing, which is probably a function of the viscosity of the material. Thus
the sample was annealed just below the clearing point. After 24 h, large areas
of the preparation evolved to show fingerprint defects and the Grandjean plane
Fig. 54 Chiral supermolecular fullero-dendrimer 46