Supermolecular Liquid Crystals - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 14

nematic phases, whereas for terminal attachment (end-on) smectic phases
appear to predominate, as shown in Fig. 15.
In addition to number density and orientation of attachment, the degree
to which the mesogenic units are decoupled from the central structure is im-
portant. The shorter the linking unit, the more likely the material will act as
a single supermolecular entity, whereas the longer the spacer the more likely
it is that the properties of the individual mesogenic groups will dominate the
overall properties of the material.
Apart from these coarse property-structure-activity relationships, a sec-
ondary level of structure needs to be considered in defining the finer points of
such relationships. For example, the central scaffolds might be considered to
be soft (flexible) or hard (rigid), there might be blocks of mesogenic groups
of one type or another, there could be microphase segregating units incor-
porated into the periphery or the scaffold of the material, mesogenic units
might be incorporated into the scaffold as well as the periphery, it is also pos-
sible to incorporate metallomesogenic units as well as conventional organic
mesogenic moieties, and chirality might be introduced into any part of the
structure. Figure 16 shows some examples of templates for supermolecular
Fig. 15 Orientation of attachment of rod-like mesogenic groups to a central scaffold and
mesophases formed for supermolecular systems, shown in comparison to the structures
of side-chain liquid crystal polymers