Discontinuous micellar cubic phase

The surfactant exit rate constant from the aggregates present in the discontinuous (micellar) cubic phase formed by some surfactants at high concentration has been determined by NMR self-diffusion, The reported values of k compare well with those obtained in the case of micellar solutions. 

Micellar cubic (OD), hexagonal columnar (ID), lamellar (2D), and bicontin-uous cubic (3D) nanostructures are formed by self-assembly of 13. For the complexes with IiC104, the ionic conductivities show discontinuous changes following the phase transitions with change of temperature or molecular structure of the dendritic moiety. For example, the conductivity of the complex of 13 with LiC104 drops from 4.6 x 10 6 to 1.2 x 10 9 S cm, along the phase transition from crystalline lamellar to micellar cubic phases. 

In contrast to the bicontinuous cubes, the less studied micellar cubic phases have positive Gaussian interfacial curvatures and are discontinuous, consisting of discrete micellar aggregates [164]. The structure of four micellar cubic phase has so far been established. 

In an additional study by Yuli-Amar et al., in order to achieve low-viscosity reverse hexagonal phases at room temperature, ethanol and diethylene glycol monoethyl ether (Transcutol) were added to the ternary GMO/TAG/water mixture [29], These studies were based on findings showing that alcohols can destroy liquid-crystal phases, and ethanol and PEG were shown to form discontinuous micellar cubic and sponge phases instead of bicontinuous phases (49-51). It was shown that the addition of Transcutol or ethanol to the GMO/TAG/water mixture enabled the formation of a room temperature fluid Hn phase. 

Figure 4.11 Schematic representation of spherical reverse micellar structure formed in discontinuous cubic (b) phase. The radius of the micelle is r, the radius of the hydrophilic...

Figure 3.4 The temperature-concentration phase diagrams of BPS-m (m=5,10,20, and 30) with BmimPFj. The phase abbreviations are as follows micellar phase (1 ), discontinuous cubic liquid crystal phase (1 ), hexagonal liquid crystal phase (H ), lamellar liquid crystal phase (L ), lamellar gel phase (L ), reverse micellar phase (L ), ionic liquid phase (IL), and two-phase separation (II). The chemical structure of j0-sitosterol ethoxylates as a typical example of BPS-m is also shown in this figure. Reproduced from Sakai et al. [37] with permission from Japan Oil Chemists Society.

In the presence of water, surfactants and lipids give rise to a variety of phases referred to as lyotropic phases or mesophases.i The most important of these phases are the lamellar, hexagonal, cubic micellar, and cubic bicontinuous phases denoted by L, H and V, and Q, respectively (see Figure 1.11 in Chapter 1). The subscripts 1 or 2 attached to these phase symbols indicate that the phase is direct (water continuous) or inverse (discontinuous water domains). Many other lyotropic phases have been identified that differ from the main ones by the state of the alkyl chain (crystalline or disordered) and of the head group arrangement (ordered or disordered). In the particular case of the lamellar phase, additional variations come from the possible different orientations adopted by the alkyl chains with respect to the plane of the lamellae (angle of tilt of the chain) and also from the state of the surface of the lamellae that can be planar or rippled. Numerous detailed descriptions have been given for the equilibrium state of the various phases that surfactants and lipids can form in the presence of water. 

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