The HLD‐NAC Model for Mixtures of Ionic and Nonionic Surfactants

Abstract

The HLD-NAC model has been used as an ''equation of state'' to predict the properties of microemulsion (lE) systems formulated with either anionic or nonionic surfactants. The model uses the concept of the hydrophilic-lipophilic difference (HLD) to calculate the chemical potential difference of transferring a surfactant from the oil to the aqueous phase; as a function of formulation variables such as type of surfactant, oil, temperature, electrolyte concentration. The value of HLD is used as a scaling parameter to calculate the net and average curvatures (NAC) of the surfactant at the water/oil interface. These curvatures determine the phase volumes, phase transitions, and solubilization capacity of lEs. In this work, the HLD-NAC model is extended to nonideal surfactant mixtures of anionic and nonionic surfactants. The phase behavior of limonene lEs formulated with binary mixtures of sodium dihexyl sulfosuccinate with nonionic nonylphenol ethoxylates and alcohol ethoxylates was used to determine the deviations of the HLD from the ideal mixing behavior. The deviations were fitted using a 2-parameters Margules equation. The results suggests that the deviations in anionic-rich systems are due to the charge shielding effect of nonionic surfactants, and in nonionicrich systems, the deviations seem to be explained by the increase in hydration of the surfactant headgroups due to the presence of anionic surfactants. When these corrections were used to predict the curvature of dioctyl sulfosuccinate-dodecyl pentaethylene glycol-heptane lEs, the HLD-NAC model corrected for the nonidealities reproduced not only the trends but also the actual range of values reported in the literature.

Partitioning behavior of an acid-cleavable, 1,3-dioxolane alkyl ethoxylate, surfactant in single and binary surfactant mixtures for 2- and 3-phase microemulsion systems according to ethoxylate head group size

“…Consistent with this trend is the slightly higher aqueous phase concentration of CK-2,13-E 5.6,ave ( Table 2). In agreement, a recent thermodynamic study concluded for the nonylphenyl ethoxylate/sodium dihexyl sulfosuccinate binary system that the latter increases hydration of the ethoxylate groups, which would increase their polarity, hence promoting their partition to the aqueous phase [37]. In contrast, the contribution of CK-2,13s hydrophobic moiety toward partitioning was not strongly affected by C8bG1 or AOT, evidenced by log K 0,HLB values for the binary surfactant systems and CK-2,13-E 5.6,ave single-surfactant system being similar (Table 5).…”

Low-energy formation of edible nanoemulsions: Factors influencing droplet size produced by emulsion phase inversion

“…1. A change in the nature of the oil phase would be expected to change the HLD number of the surfactant, i.e., its relative affinity for the oil and water phases [13,31]. In turn, a change in the surfactant HLD number would be expected to alter various physicochemical properties that impact nanoemulsion formation: the distribution of surfactant molecules between the aqueous and organic phases; the spontaneous formation of fine oil droplets at the aqueous-organic phase boundary; the coalescence stability of the droplets.…”

“…In turn, a change in the surfactant HLD number would be expected to alter various physicochemical properties that impact nanoemulsion formation: the distribution of surfactant molecules between the aqueous and organic phases; the spontaneous formation of fine oil droplets at the aqueous-organic phase boundary; the coalescence stability of the droplets. For example, as the HLD number moves towards zero, there is usually a decrease in oil-water interfacial tension in a SOW system, which facilitates the spontaneous formation of fine oil droplets [29,31,32]. On the other hand, as the HLD number tends towards zero, the rate of droplet coalescence in SOW systems usually increases, which would cause any fine droplets formed to rapidly grow in size [10,30].…”

Evaluating the hydrophilic–lipophilic nature of asphaltenic oils and naphthenic amphiphiles using microemulsion models

“…In other words, naphthenic acids are more hydrophilic than oleic acid. Another interesting point of comparison is that sodium oleate, the salt of oleic acid, has a C C of À1.7 [45]. In this case, the neutralization of the fatty acid produced a decrease in C C of 1.7.…”