Liquid Crystalline Assembly of Rod–Coil Molecules - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 83

Fig. 13 Structural analysis of the supramolecular bundles assembled from molecular
dumbbells 19 - 21
the dissimilar parts of the molecule [32, 33, 80, 81]. Anisotropic ordering of
the rod building blocks in the molecule should exclude chemically dissimi-
lar dendritic segments. Because dendritic wedges have a large cross-section,
they will encounter strong repulsive forces when trying to accommodate the
density of the ordered rod building blocks. These repulsive forces could bal-
ance the favorable aggregation of rod building blocks and generate the finite
aggregation of dumbbell-shaped molecules. As the cross-sectional area of
the dendritic wedges increases, so do the repulsive forces between them.
Consequently, this increase in steric repulsion could give rise to smaller ag-
gregates that allow more space for the dendritic building blocks to adopt
alessstrainedconformation.
If supramolecular bundles are formed spontaneously in bulk films, by in-
clusion of appropriate reactive groups it should be possible to convert these
into molecular objects by cross-linking, while maintaining the precise size
and shape of the rod bundles. A coil-rod-coil triblock molecule 22 based on
linear PPO ( f coil = 0.73) with a reactive rod block self-assembles into discrete
rod bundles that are encapsulated by PPO coils and subsequently organize