Phase behavior, solubilization, and phase transition of a microemulsion system stabilized by a castor oil-based novel surfactant (sodium methyl ester sulfonate) and cosurfactant (propan-2-ol) were investigated for effective application in oil recovery processes. A pseudoternary phase diagram showed the existence of different phases (S/L phase, Winsor I, Winsor II, Winsor III, and Winsor IV) by conventional titration method. With an increase in the cosurfactant-to-surfactant ratio (Kcs), the region under the Winsor III phase was found to increase. An increase in cosurfactant content in the system mixture improved interactions of the surfactant with oil and water in the microemulsion phase, thereby reducing molecular aggregations in solution. At optimal salinity, equal amounts of oil and water were solubilized in a microemulsion in the Winsor III systems and showed ultralow interfacial tension (IFT) values on the order of 10–3 to 10–4 mN/m. Phase dilution studies revealed that the microemulsion systems form...

Phase Behavior, Solubilization, and Phase Transition of a Microemulsion System Stabilized by a Novel Surfactant Synthesized from Castor Oil

In commercial formulations, surfactants are often co-formulated with inorganic electrolytes, which are included as inexpensive thickeners. Salts affect the surfactant’s aggregative and functional behavior. However, while the electrolyte effect on the self-aggregation of ionic surfactants can be rationalized in terms of electrostatic interactions, in the case of nonionic surfactants the molecular determinants are still unclear. In this work, we investigate the effects of alkali and alkaline–earth metal chlorides on the micellization of the nonionic surfactant hexyl penta(oxyethylene) ether, C6E5, in aqueous solution. To this aim, the C6E5 intradiffusion (also named self-diffusion) coefficient in aqueous mixtures of various alkali and alkaline–earth metal chlorides was measured by pulsed gradient spin-echo NMR. The results show that all the considered electrolytes cause a decrease of the surfactant critical micellar concentration, cmc, while the micellar size is almost unaffected. The experimental evidence can be interpreted in terms of de-hydration of the apolar alkyl tails with a minor contribution arising from the dehydration of the poly(ethylene oxide) headgroups. The order of effectiveness of the different cations follows the Hofmeister series, some aspects of which are briefly discussed.

Effects of Salts on the Micellization of a Short-Tailed Nonionic Ethoxylated Surfactant: An Intradiffusion Study

A theoretical spinodal curve for the system water + chloroform + acetic acid at 25 °C is derived using a lattice model for ternary amphiphilic solutions: rod-like molecules covering the bonds of the honeycomb lattice with three-body interactions between the molecular ends associated to the same lattice site. The molecular model is equivalent to the standard Ising model on the same lattice; its mean-field solution is the most appropriate for reproducing, by local fitting, the experimental data for the binodal composition. The derived spinodal curve is in very good agreement with the spinodal composition determined also in the present work from the measured diffusion coefficients recently reported for the same system.

https://rd.springer.com/content/pdf/10.1007%2Fs10953-009-9384-5.pdf

Spinodal Composition of the System Water + Chloroform + Acetic Acid at 25 °C

Plait point in ternary system with a miscibility gap: Analysis of the procedures involved in its determination and development of novel procedures

The ferromagnetic–ferrimagnetic ternary alloy described in the form of $$AB_{p}C_{1-p}$$
 consisting of spins $$S_i^A=1/2$$
 , $$S_j^B=3/2$$
 and $$S_j^C=5/2$$
 is studied in the framework of the mean field theory (MFT) based on the Bogoliubov inequality for the free energy. The model has a selective site disorder, i.e., $$S_i^A$$
 can either have $$S_j^B$$
 as the nearest neighbor with probability p or $$S_j^C$$
 with $$1-p$$
 randomly. The ground-state phase diagrams are calculated on the (
 $$R=\vert J_{AC} \vert /J_{AB},d=D/zJ_{AB})$$
 planes to reveal various possible ground states of the system. The phase diagrams are mapped on the $$(R,kT_{c}/J_{AB})$$
 , $$(D/J_{AB},kT_{c}/J_{AB})$$
 , $$(p, kT_{c}/J_{AB})$$
 and $$(p, kT_{comp}/J_{AB})$$
 planes for given values of p, R and D. It is shown that the model only displays second-order phase transition temperatures. The existence of single or double compensation temperatures is also evident for the appropriate values of our parameters. We have also confirmed the existence of multicompensation behavior for the total magnetization of the system via the application of Monte-Carlo (MC) simulations as predicted by the MFT approach. Our obtained results are compared to those reported in the literature and reliable agreements are found.

The critical behaviors of a ferromagnetic–ferrimagnetic Ising ternary alloy with mixed spin-( 1/2, 3/2, 5/2)

A model is considered in which the bonds of a honeycomb lattice are covered by rodlike molecules of types AA, BB, and AB. Neighboring molecular ends have three-body and orientation-dependent interactions. The model is shown to be equivalent to a spin-1/2 Ising model on the same lattice with a field, but with only pairwise interactions. Symmetric and asymmetric coexistence surfaces for the separation into an AA-rich and a BB-rich phase are calculated exactly.

An exactly solvable model for a ternary solution with three-body interactions and orientationally dependent bonding.

We consider the class of Hamiltonians composed by a quadratic form in the canonical operators and a linear interaction term with time periodic external fields of an arbitrary strength. The Hamiltonian can be made time independent by a unitary transformation in the extended Hilbert space, which has the meaning of a time-dependent translation in the classical phase space. We solve the eigenvalue problem for the Floquet Hamiltonian and we find general expressions for the time-dependent wave functions, of interest for the optical and transport properties of quantum nanostructures.

The Floquet Solution for Systems with Quadratic Form Hamiltonians

A new method is presented to obtain a theoretical spinodal for ternary solutions with an amphiphile component. This method uses a generalized Wheeler-Widom model representing the ternary solution, and considers local fitting conditions with the experimental binodal, imposing that the theoretical binodal must pass through a point on the experimental binodal, and also that the slope of the theoretical binodal has to be as close as possible to the slope of the representative experimental binodal. Using the previously specified fitting conditions, the corresponding spinodal is derived. The results are in agreement with an older method of local fitting between the generalized Wheeler-Widom model and the experimental data, where the fitting condition implied the coincidence of the theoretical tie-line with the experimental tie-line.

Radu P. Lungu

Papers

An exactly solvable model for a ternary solution with three-body interactions and orientationally dependent bonding.

Spinodal Composition of the System Water + Chloroform + Acetic Acid at 25 °C

Plait point in ternary system with a miscibility gap: Analysis of the procedures involved in its determination and development of novel procedures

The Floquet Solution for Systems with Quadratic Form Hamiltonians

New Method for Theoretical Spinodals Corresponding to Ternary Solutions with an Amphiphile Component