Emulsion phase diagrams

Nevertheless, possibiUties for confusion abound. From the definitions of microemulsions and macroemulsions and from Figure 1, it immediately follows that in many macroemulsions one of the two or three phases is a microemulsion. Until recentiy (49), it was thought that all nonmultiple emulsions were either oil-in-water (O/W) or water-in-oil (W/O). However, the phase diagram of Figure 1 makes clear that there are six nonmultiple, two-phase morphologies, of which four contain a microemulsion phase. These six two-phase morphologies are oleic-in-aqueous (OL/AQ, or O/W) and aqueous-in-oleic (AQ/OL, or W/O), but also, oleic-in-microemulsion (OL/MI), microemulsion-in-oleic (MI/OL), aqueous-in-microemulsion (AQ/MI), and microemulsion-in-aqueous (MI/AQ) (49). 

Figure 1.4. For a nonionic surfactant, influence of the temperature on (a) the surfactant morphology and hence the spontaneous curvature, (b) the type of self-assembly, (c) the phase diagram, the number of coexisting phases is indicated (d) the coexisting phases at equilibrium, and (e) the corresponding emulsions.

Figure 3.5. Phase diagrams obtained for two monodisperse water-in-oil emulsions stabi-hzed with SMO. (O) totally dispersed (O) flocculated (fluid-sohd) ( ) totally flocculated (gel). (Adapted from [11].)...

A considerable amount of experimental work has been carried out on the so-called gel emulsions of water/nonionic surfactant/oil systems [9-14, 80, 106, 107]. These form in either the water-rich or oil-rich regions of the ternary phase diagrams, depending on the surfactant and system temperature. The latter parameter is important as a result of the property of nonionic surfactants known as the HLB temperature, or phase inversion temperature (PIT). Below the PIT, nonionic surfactants are water-soluble (hydrophilic form o/w emulsions) whereas above the PIT they are oil-soluble (hydrophobic form w/o emulsions). The systems studied were all of very high phase volume fraction, and were stabilised by nonionic polyether surfactants. 

Figure 7.10 Effect of the thermodynamic incompatibility of otsi/p-casein + high-methoxy pectin (pH = 7.0, / = 0.01 M) on phase diagram of the mixed solutions and elastic modulus of corresponding casein-stabilized emulsions (40 vol% oil, 2 wt% protein), (a) (O) Binodal line for p-casein + pectin solution with critical point ( ) ( ) binodal line for asi-casein + pectin solution with critical point ( ). (b) Complex shear modulus G (1 Hz) is plotted against the pectin concentration (O) p-casein ( ) o i -casein. Dotted lines indicate the range of pectin concentration for phase separation in the mixed solutions. The pectin was added to the protein solution before emulsion preparation. Data are taken front Semenova et al. (1999a).

Figure 12.15 Phase diagram of a vater-in-octane-C12E5 emulsion. The axes are temperature and volume fraction of surfactant. The phases are indicated by 3 (three-phase-region), Li, L2, and Lq. (lamellar). The phase diagram was determined for a volume ratio between water and octane of 1 1 [561]. The phases observed along the vertical arrow at 4>s = 0.15 are shown schematically at the bottom. Results were obtained by D. Vollmer.

H T2 relaxation experiments have moreover been used to investigate the phase composition, interfaces and phase diagrams of polymer solutions, emulsions and coreshell lattices [167-173]. 

The interfacial tension y at the planar interface has a minimum near the temperature Indeed, at the latter temperature r is small, A/jt0 = 0 and because d ij w/d J and dfi /dT have opposite signs and s is also small (because T is small), dy/d I 0. The temperature T0 is provided by Eq. (25) and is independent of the concentration of surfactant. In other words, the two minima of Fig. 4 which correspond to the phase inversion temperatures of a macroemulsion (the curve with a positive minimum) and microemulsion (the curve with a negative minimum) are the same. When emulsions are generated from a microemulsion and its excess phase, the emulsion is of the same kind as the microemulsion, the phase inversion temperature is obviously located in the middle of the middle phase microemulsion range and the above conclusion remains valid. The above results explain the observation of Shinoda and Saito [6,7] that the phase inversion temperature (PIT) of emulsions can be provided by the ternary equilibrium phase diagram. 

FIGURE 4.25 Three-component phase diagram for the solubilization. Cre, Cremophor RH 40 Gly, glyceride Pol, poloxamer 124 L, isotropic microemulsion G, gel E, crude OAV emulsion E2, W/O emulsion. [Graph reconstructed from data by Kim et al. Pharm. Res., 18, 454 (2002).]... 

The phase relationships of two-phase polymer systems also have been of considerable interest in recent years. In an important series of papers, Molau and co-workers (19-24) studied systems, which were denoted POO emulsions (polymeric oil-in-oil), prepared by dissolving a given polymer in monomer and then polymerizing the monomer. During polymerizations of this type the composition of the respective phases reverses, and a phase inversion process was proposed to explain this. A similar process has been suggested as the mechanism by which poly-butadiene forms the dispersed phase in the manufacture of high-impact polystyrenes (22,25). Recently, Kruse has pointed out that this phase-inversion point may correspond to that point on a ternary phase diagram at which the reaction line bisects a tie line (26), and we have advanced a similar point of view in our earlier reports (17,18, 27). 

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