Rhombohedral mesh phases

Exotic phases are found at compositions between lamellae and hexagonal cylinders (see Figs. 12-19 and 12-20). Some examples of the morphologies of these phases are shown in Fig. 12-22 these include cubic strut phases, tetragonal and rhombohedral mesh phases, and rectangular ribbon phases. 

Figure 12. Schematic representations of (a) centered rectangular phase, (b) representation of six connected rhombohedral mesh phase.

Figure 13. The X-ray scattering from a 52 wt% CigEOg/ water sample, (a) Lamellar phase (b) random mesh phase (c) rhombohedral mesh intermediate phase (d) Ia3d cubic phase and (e) hexagonal-f-gel two phase region.

The relative stability of mesh and IPMS structures is still unclear. For example, the Ri mesophase (of rhombohedral symmetry) in the SDS-water system transforms continuously into the neighbouring bicontinuous cubic phase (Fig. 4.14) [20]. This suggests that this mesophase is a hyperbolic (reversed) bilayer Ijring on a rhombohedral IPMS. Indeed, the rhombohedral rPD surface is only marginally less homogeneous than its cubic counterparts, the P- and D-svu-faces. 

In addition to 3D columnar packings, these branched polycontinuous forms include novel mesh structures, with 3D arrangements of meshes, rather than the smectic array common to the R and T mesh mesophases. One example, a rhombohedral arrangement of the hexagonal mesh (found also in the R phase), is shown in Figure 16.26. 

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