Hierarchically Organized Systems Based on Liquid Crystalline Phases - Self-Assembled Supramolecular Architectures: Lyotropic Liquid Crystals - page 156

Figure 6.1 Diversity and tuning of lipid polymorphism. Amphiphilic molecules such
as lipids have a hydrophilic head group and a long hydrophobic alkyl chain. These
molecules self-assemble in aqueous media; according to their molecular shape they
form type 0, 1, or 2 micelles, typical examples of which are biological membrane, deter-
gent, and lipid assemblies, respectively (top right). The original molecular shape can be
modulated by certain parameters, such as temperature, pressure, water, and composi-
tion (see bottom left). An increase in the inverse conical shape of a molecule, typical
for type 2 micelles, increases the average negative mean curvature of the lipid meso-
phases from lamellar toward the L 2 phase via the cubic Im3m, Pn3m, and Ia3d phases,
hexagonal, and micellar cubic Fd3m phases, as shown here. Schematic drawings of
these (most common) phases show the 1, 2, and 3 dimensionality of the lipid phases
(diagonal).

the inverse conical shape of the molecule, which results in more negatively
curved mesophases (Fig. 6.1). The lipid molecular shape can also be engineered
by altering the unsaturation (number and location), which thus provides an
opportunity to fi nely control the lipid phase behavior (Kulkarni et al., 2010c).
More lipid phases can be formed by adding other chemical components
(Faham and Bowie, 2002; Guillot et al., 2006; Kulkarni et al., 2011b; Misquitta
and Caffrey, 2001; Yaghmur et al., 2006, 2007). Thus, with the varying physico-
chemical nature of the amphiphiles, and with varied parameters such as tem-
perature and composition, an assortment of polymorphs can be observed, as
shown in Figure 6.1 (see also Fig. 6.2). Due to their dimensional range (from
∼ 2.5 to 25 nm) and their solid-liquid mediation, they are also called liquid

crystalline (LC) nanostructures, which can be further developed into fascinat-
ing superstructures.