Formation of liquid crystal and other non-fluid phases in emulsions containing non-ionic surfactants

Abstract

The relation between the phase distribution of components and the nature and properties of dispersions formed in a four-component system containing dodecane, water and two homogeneous non-ionic surfactants has been investigated by phase-rule techniques. Phase equilibrium diagrams for the four ternary systems were investigated and the phase boundaries for the various regions formed in these systems were defined by synthetic and analytical methods. In some of the ternary diagrams a narrow three-phase region occurs where 'gel' or liquid crystal as well as two isotropic liquid phases are present. Dispersions containing the gel phase were very stable. The four-component system has not been fully investigated due to the presence of extensive liquid crystal phases and three-phase regions. However, some distribution data for the quaternary system was obtained. In the presence of sufficient amounts of the short chain non-ionic surfactant C,,H,,(O.CHz.CHz),OH, a three-liquid phase region occurs where multiple drops readily form.flthough emulsions are usually treated as twoliquid phase dispersions there is a growing body of evidence that a third phase is commonly present md some results show that the stability and other properties of emulsions are entirely controlled by this phase, which usually takes the form of a gel or is liquid crystalline (see Marland & Mulley, 1971 a d refs cited). Even in the systems belonging to the two-phase class, the disperse phase may not be a simple liquid but a phase in the liquid crystal state. For most members of the ionic and non-ionic classes of synthetic surfactants used in pharmacy, the concentration range of the emulsifying agent forming simple liquid-liquid dispersions is often extremely limited (below 1 "A, and this is probably also true of many surfactants used in other fields. Further phase-rule studies on model systems are required to delineate the relation between component composition, the number and nature of the Phases present and the surfactant distribution, because this information is essential to an understanding of the factors controlling emulsion type In the present paper two non-ionic surfactants %I & and C,,E,(see Mulley, 1967 for an explanation of the nomenclature) have been investigated in dodecane-water dispersions. This mixture of low mokular weight emulsifying agents approaches

Phase Behavior of Aqueous Mixtures of Some Polyethylene Glycol Decyl Ethers Revealed by DSC and FT-IR Measurements

“…The phase states assumed in each temperature region, which were determined by referring the phase diagrams (Figs. [3][4][5], are also indicated in the figure.…”

Weakly charged lamellar bilayer system: Interplay between thermal undulations and electrostatic repulsion

“…The molecular mass of C 10 E 3 is: M 0 = 290.5 g/mol. Values of density: ρ 0 = 0.936 g/cm 3 , critical micelle concentration: cmc = 4.2 × 10 −4 mol/l (at T = 25 • C), and refractive index: n 0 = 1.4453 (at 25 • C and wavelength 589 nm) were taken from literature [6,28]. The ionic surfactant sodium dodecyl sulfate (SDS), used to charge the membranes, was synthesized and purified in our laboratory to a purity of better than 99%.…”

“…With this in mind, we have recently studied the effect of adding a cationic polyelectrolyte to the highly dilute lamellar L α -phase formed by the non-ionic surfactant triethylene glycol monodecyl ether (C 10 E 3 ) in water [5]. At temperatures below 30 • C this surfactant forms a lamellar bilayer phase that is stable down to about 1 wt% of surfactant [6,7]. At such extremely low surfactant weight fractions, the interlamellar spacing is of the order of the wavelength of visible light, i.e.…”

Effect of molecular weight of triglycerides on the formation and rheological behavior of cubic and hexagonal phase based gel emulsions

“…It is known that HIPREs can form in the water (O/W) and oil (W/O) rich region under certain conditions [2,[9][10][11]. Due to their characteristic features such as high volume fraction of the internal phase, high viscosity, and transparency, they are also referred to as gel emulsions [1,3,12,13].…”