Inverse hexagonal phase

Fig. 4.44 Phase diagram for aqueous solutions of Pluronic P104 (PEOi7PP05,PFX)27) (Noolandi et al. 1996). Notation iso, isotropic (polymer poor) solution cubic, cubic phase hex[, hexagonal phase lam, lamellar phase, hex2, inverse hexagonal phase, cubicj, inverse cubic phase, iso2, isotropic (polymer rich) solution. The solid and dashed lines are calculated from the continuum and lattice versions of self-consistent field theory respectively.

Tate, M. W., Shyamsunder, E., Gruner, S. M., and D Amico, K. L. (1992). Kinetics of the lamellar-inverse hexagonal phase transition determined by time resolved x-ray diffraEBochemistry, 31,1081-1092. 

The aggregation behavior of AB silicone surfactants in nonpolar oils including several hydrocarbon oils has been reported by Rodriguez [46]. They found that inverse micelles were formed in all oils, adjacent to the inverse cubic phase formed by the neat copolymers and by concentrated mixtures of copolymer and oil. The CMC depended strongly on the length of the pEO chain but only weakly on the pDMS chain. Inverse hexagonal phase was also observed. 

Figure 12.24 Phase diagrams for (a) 1-monoolein in water and (b) di-dodecyl alkyl-j8-D-glucopyranosyl-rac-glycerol in water, Hn is the inverse hexagonal phase, Gn is the inverse gyroid Ia3d, and Du is the inverse double-diamond Pn3m phase. In the inverse phases, the aqueous phase is inside the channels. [Part (a) Reprinted with permission from Larsson et al.. Journal of Physical Chemistry 93 7304 Copyright 1989, American Chemical Society. Part (b) Reprinted with permission from EDP Sciences.]...

Cubic strut phases are common in the phase diagrams of two-tailed surfactants. These surfactants have a relatively high value of the vfaolc parameter, because the volume-to-length ratio v/i(. of the double tail is twice that of a single tail. A high value of v/aoic is consistent with the formation of type II bicontinuous and other inverse phases, such as the inverse hexagonal phase in Fig. 12-24. 

Monoglycerides form an inverse hexagonal phase with glycerol, as in water [112], Mixtures of triethanolamine and oleic acid form a nonaqueous lamellar liquid crystal with a surfactant bilayer of soap and acid with intercalated ionized and unionized alkanolamine as solvent [113,114], Lamellar liquid crystals form analogously with dodecylbenzenesulfonic acid and triethanolamine [115]. 

All three additives have roughly the same alkyl chain length and volume as sodium octanoate (decanol is just a bit bigger). The phase behavior of octanol/sodium octa-noate/water is available but the decanol system has received the most attention by far. We see that decanol mixes in the system to form a large lamellar region, and even an inverse hexagonal phase. This is because the alcohol group always resides at the water/... 

Figure 2 Phase diagram of a binary amphiphile-water mixture obtained from a Ginzburg- Landau model with a vector order parameter for the amphiphile orientation (50,51]. The phases L and L2 are micellar liquids, is a lamellar phase. H and H denote hexagonal and inverse hexagonal phases, respectively, I is an fee crystal of spherical micelles, and V is a simple cubic bicontinuous phase. (From Ref. 51.)...

Although such siloxane surfactants were extensively exploited, their surface active properties are still investigated [21, 27, 44], All types of aggregates known for hydrocarbon surfactants comprising micelles, lyotropic liquid crystalline phases from lamellar to the inverse hexagonal phase, vesicles, and "sponge" (L3) phases have been found in aqueous solution [37, 45]. 

Most of the PILs displayed fewer lyotropic liquid crystalline phases than were observed in aqueous systems. There were some differences in the thermal stability ranges of the liquid crystalline phases, particttlarly the inverse hexagonal phase for myverol and phytantriol, whose onset temperature is 84 or 44 °C in water, respectively, and was seen from below room temperature in many of the PILs. ... 

Figure 30 Schematics of the lyotropic liquid crystals used in the study, depicting periodically ordered hydrophilic and hydrophobic domains (a) hexagonal phase, (b) lamellar phase, and (c) inverse hexagonal phase. Hydrophilic domains are dark-colored, hydrophobic domains are light-colored, and TEM micrographs of Bi nanoparticles produced by shear-mixing lyotropic liquid crystals containing 0.05 M BiCls and 0.4 M C1CI2 as the aqueous component, (d) Hexagonal phase, (e) lamellar phase, and (f) invase hexagonal phase. (Reproduced from Ref. 101. American Chemical Society, 2004.)...

Figure 11.25 Schematic phase diagram of a binary system surfactant/water. Inverse hexagonal phase Hn, lamellar phase Lo, hexagonal phase Hj, isotropic (cubic) phases a, b, c, d.

Figure 4.26 Sequence of phases observed on increasing solvent content, in a binary amphiphile-solvent system, representing a hypothetical phase diagram where phase transitions are controlled by solvent content only. Here a, b, c and d indicate intermediate phases (for example the bicontinuous cubic structure shown in Fig. 4.25d), L2 denotes the inverse micellar solution, Hn is the inverse hexagonal phase, L is the lamellar phase. Hi is the normal hexagonal phase and Li is the normal micellar phase. In practice, the full sequence of phases is rarely observed, and in reality the phase transitions depend on temperature as well as concentration...

In the Hii phase, which can be interpreted as an inverse hexagonal phase, the lipid mono-layers form long cylinders with the apolar tails directed toward the periphery of the structure. Thus, several cylinders can make a periodic arrangement of Hn phases in which the apolar tails of one cylinder interact with those of its immediate neighbor (Fig. 2.16). 

Inverse hexagonal phase (H2) formed from rod-like water channels in an amphiphilic matrix... 

Inverse phases such as w/o micelles and inverse hexagonal phases are unique because they place high functional group density toward a core or narrow channel, respectively, and this density can provide unique reactivity [171]. W/o micelles are spherical entities made by dissolving an ampMphile in an oil/water mixture. Under these conditions, the polar headgroup of the amphiphile partitions at the oil-water... 

Simmons et al. studied the kinetics of the phase transition L Hg (inverse hexagonal phase) in a leci-thin/AOT/water/isooctane system where the isooctane makes up the continuous phase, using TR-SANS. The time constant for the transition was reported to be about 420 s. However, the temperature quench across the L/Hg coexistence region was very large (> 40°C) and relatively slow (about 100 s). Both effects may have much affected the reported time constant. 

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