Polymer-surfactant systems, phase diagram

The Polymer, Surfactant, Salt phase diagram (11b) shows overall less coacervate than the Salt, Surfactant, Polymer diagram (11a) and the No Salt diagram. In this experiment, the polymer and surfactant were allowed to mix before salt was added, which promotes ion-exchange interactions. However, once the salt was added, the chemical potential of the system shifts such that ion-exchange is reversed which leads to a resolubilization of the coacervate formed via electrostatic interactions at some compositions. 

Lochhead RY, Warfield DS, Gasiewski C. Phase diagrams as a formulation guide in aqueous polymer/surfactant systems. Polym Eng Sci 1985 25 1110-1117. 

Lindman, B., Carlsson, A., Gerdes, S., Karlstroem, G., Piculell, L., Thalberg, K., et al. (1993). Polysaccharide-surfactant systems interactions, phase diagrams and novel gels. In Dickinson, E., Walstra, P. (Eds). Food Colloids and Polymers Structure and Dynamics, Cambridge, UK Royal Society of Chemistry, pp. 113-125. 

FIG. 8.13 Two representations of a portion of the phase diagram for the water-benzene-potassium oleate-pentanol system. The unshaded regions represent homogenous solutions, (a) Redrawn, with permission, from S. Friberg and I. Burasczeska, Prog. Colloid Polym. Sci., 63, 1 (1978). (b) Redrawn, with permission, from C. U. Herrmann, U. Wurz, and M. Kahlweit, In Solution Chemistry of Surfactants, Vols. 1 and 2 (K. L. Mittal, Ed.), Plenum, New York, 1979. 

Karlstrom, G. Carlsson, A. Lindman, B., "Phase Diagrams of Nonionic Polymer-Water Systems. Experimental and Theoretical Studies of the Effects of Surfactants and Other Cosolutes," J. Phys. Chem., 94, 5005 (1990). 

It Is Instructive to compare these behaviors In a phase diagram (Figure 7). For all systems of polymers and particles, there Is a line of compositions where the polymers exactly saturate the surfaces of all particles. If the spheres are large. It will take many macromolecules to saturate the surface of each one If they are small, one macromolecule will saturate many spheres and hold them In a necklace. On either side of the stoichiometric line, the behaviors of oxide particles and surfactant micelles diverge ... 

Figure 4.9 Phase diagram of the system water-decane-CioE4 at equal volume fractions of water and decane as a function of the temperature T and the surfactant concentration cf>7. At low (f>7 there is a three-phase coexistence, while at moderate cf>7 the one-phase bicontinuous microemulsion appears. At even higher cf>7 the lamellar phase appears. At high and low temperatures a microemulsion phase coexists with either excess water or oil. The polymer fraction cf>p is raised symmetrically for the water- and oil-soluble polymers, and the one-phase microemulsion window closes continuously. The 2 K temperature shift is due to the use of heavy water. (From Ref. [40], reprinted with permission of the American Chemical Society.)...

Figure 4.12 Phase diagram of the system water-isooctane-AOT-PEO as a function of the temperature T and the surfactant concentration y. The isooctane content was fixed at 40wt.% and the polymer content in the aqueous phase was either Cp = 5 or 20 wt.%. The phase regions are 2 for microemulsion coexisting with excess water, 2 for microemulsion coexisting with excess oil, 3 for three-phase coexistence of a microemulsion with two excess phases. Inside the fish-tail there are one-phase regions L Li for o/w-droplet microemulsions, L2 for w/o-droplet microemulsions, La for the lamellar phase and 2a for a coexistence of a lamellar with a microemulsion phase. Note that the whole fish-tail is shifted to higher surfactant concentrations upon polymer addition. (From Ref. [53], reprinted with permission of the American Chemical Society.)...

Fluorinated surfactants or graft polymers are typically necessary in C02 applications [48, 49]. Research into the self-assembly of these surfactants and polymers in C02 have focused on dilute systems where only reverse water-in-C02 micelles are expected [39, 50-52, 53]. Regions of the phase diagrams where C02-in-water micelles, bicontinuous microemulsions or liquid crystalline phases are formed remain to be investigated in detail. There is only one system known so far where all these phases have been observed. We will come back to this at the end of Section 7.4. The properties of reverse micelles in C02... 

As for low molecular weight surfactants, the superstructures are assumed to be formed by micellar aggregates [126], But it seems that the formation of lyotropic liquid crystals is supported by the additional presence of thermotropic mesogens [87,122-124,126], Lamellar, hexagonal, cubic and even nematic and cholesteric mesophases were reported for binary systems, the latter being exceptional. Lyotropic mesophases were also observed in non-aqueous solvents [240,400,401,405], If polymerizable surfactants are studied, not only the phase diagram but also the types of mesophases observed for the monomer and the polymer may be different. 

In connection with these experiments, data are presented on how the surfactant-brine-oil phase behavior is influenced by small amounts of a polysaccharide polymer dissolved in the brine. This polymer apparently complicates phase behavior considerably in principle a fourth axis is required in the phase diagram. However, in view of the approximate nature of the ternary representation of the surfactant-brine-oil system, we shall not attempt to draw sys-... 

To describe and summarize conditions prevailing in homogeneous mixtures of an interacting (nonionic) polymer/ionic surfactant pair, where the concentration of both components changes, we utilize a phase diagram constmcted by Cabane and Duplessix (155) for the PEO/SDS system. (See Fig. 36.) In field I no complex formation occurs... 

The second (and third) models for polyelectrolyte/surfactant interaction are based on the solubility and phase characteristics of the mixed systems. The general form of the solubility diagram of a polyelectrolyte/oppositely charged surfactant system, as illustrated by the Polymer JR/TEALS combination, has been referred to (57). It showed an intermediate zone of precipitation, but clarity for high (and low) concentrations of the surfactant. The line representing systems of maximum insolubility in the log polymer/log surfactant concentration plot had a 45° slope indicating constant composition of the insoluble complexes. 

Phase diagram calculations are carried out for a given set of the five parameters by the conventional procedure of minimizing the total free energy with respect to the content of the three components in the different phases. Despite the need for severe assumptions (for example, component 2, the surfactant, has to be treated as a second polymer) and the large number of adjustable parameters, it was found possible to obtain reasonable approximations to the acmal behavior of mixed systems. 

The SANS technique was further adopted to study the partitioning of monomer between microemulsion droplets and polymer particles for various monomers (ST, w-butyl methacrylate, -butyl methacrylate, and CeMA) (34). It was found that, during microemulsion polymerization, the partitioning of monomer is strongly dependent on the composition of microemulsion, especially on the distance to the phase boundary in the pseudo three-phase diagram of the surfactant/cosurfactant-oil-water system. For example, the monomer partitioning is linear in nature and the concentration of monomer in polymer particles is quite low if the initial microemulsion composition is far away from the phase boundary. In contrast, the monomer partitioning is essentially nonlinear and the... 

Karlstrom G, Carlsson A, Lindman B (1990) Phase diagrams of nonionic polymer -water systems. Experimental and theoretical studies of the effects of surfactants and other cosolutes. J Phys Chem 94 5005-5015... 

The partial phase diagram at 25 °C is determined optically by titration of the oil-alcohol/surfactant mixtures with the aqueous poly(ethylene glycol) solution. The samples are stirred until the system became optically clear and ther-mostated at 25 °C in a water bath. The region of the isotropic phase is determined by dropwise addition of the polymer solution to the system. More than 20 data points are received for each phase diagram. 

FIG. 7 Idealized phase diagram for microemulsion-forming water/oil/surfactant system under well-balanced conditions. (Redrawn from A. Kabalnov, B. Lindman, U. Olsson, L. Piculell, K. Thuresson, and H Wennerstrom, Colloid. Polym. Sci. 1996, 274, 297.) The Winsor I and Winsor II microemulsions are on the right-hand and left-hand sides, respectively, of the central microemulsion region, whereas the Winsor III microemulsion is located at the downward tip. 

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