Liquid Crystalline Assembly of Rod–Coil Molecules - Liquid Crystalline Functional Assemblies and Their Supramolecular Structures - page 78

Fig. 10 Rod shape-dependent supramolecular structures
rigid aromatic, and hydrophobic docosyl chain [71]. The small-angle X-ray
diffraction pattern of 11 displays sharp reflections that correspond to a 2D
hexagonal columnar structure with a lattice constant of 8.1 nm. This di-
mension implies that the rod-like rigid segments arrange axially with their
preferred direction within a cross-sectional slice of the column, in which
docosyl chains pack in an interdigitated fashion and distort conformation-
ally (Fig. 10). In contrast, the small-angle X-ray diffraction patterns of 12
show a strong reflection together with a number of low intensity reflections
at higher angles, indexed as a 3D body-centered cubic phase with a lattice
parameter of 11.6 nm [72, 73]. Considering the space-filling requirement and
cone-shaped building block, the radial arrangement of the rigid segments is
expected to be the best way to close-pack the hydrophobic core, leading to
a discrete nanostructure. Accordingly, 12 based on a more wedge-like aro-
matic segment can be described to self-organize into an optically isotropic
cubic phase consisting of a 3D body-centered arrangement of discrete aggre-
gates, as shown in Fig. 10.
Amphiphilic molecules consisting of oligo(phenylene vinylene) (OPV)
asymmetrically end-substituted with a hydrophilic PEO segment and a hy-
drophobic alkyl chain induce self-assembly into both thermotropic and lyo-
tropic lamellar liquid crystalline phases [74]. Depending on the length of PEO
block, the mesostructures were controlled. When PEO chains are short, the
amphiphilic molecule showed a mosaic birefringence texture from polarized
optical microscopy, which is defined smectic B (S B ) mesophase. Increasing
the length of PEO chain frustrates ordering of OPV aggregation and results