Supermolecular Liquid Crystals - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 15

Fig. 16 Templates for supermolecular materials bearing A-B blocks of mesogenic units,
some of which are functionalized
materials bearing blocks of mesogenic units, some of which are function-
alized. The variety of templates available is thus very large, indicating the
potential for the development of novel materials with designer properties.
Through self-assembly and self-organization processes, liquid-crystalline
phases have opened up new perspectives in materials science towards the
design and engineering of supramolecular materials [58-61]. The self-
organization in two- and three-dimensional space offered by the liquid-
crystalline medium is an ideal vehicle to explore and control the organization
of matter on the nanometer to the micrometer scale, which are key to the
emerging development of nanotechnology.
In the following sections we describe the structures of novel polypedal,
multipedal and functional supermolecular materials.
2
Liquid-Crystalline Polypedes - Dendrimers
As noted above, various morphologies have been documented for dendritic
and hyperbranched liquid crystal polymers, and this topic has recently re-
ceived intense interest [14-27, 62-70]. Although the exhaustive revision of this
area is outside the scope of this article, several types can be easily identified:
(i) hyperbranched polymers and liquid crystal dendrimers in which the
mesogenic groups form part of each branching unit;
(ii) dendrimers without mesogenic groups that form liquid crystal phases,
where the formation of the mesophases is due to self-assembly process of
the constituent dendrons, aided by microphase segregation, and
(iii) liquid crystal dendrimers formed by attachment of liquid crystal moieties
to the periphery of a suitable core dendrimer, where the mesogenic units
arelocatedonthesurfaceofthedendriticcore.
The first thermotropic liquid-crystalline dendrimer, 15 , shown in Fig. 17, was
reported by Percec and Kawasumi for a hyperbranched polyether structure
that consisted of an AB 2 monomer, with a mesogenic unit based on confor-