Formulation in Surfactant Systems: From-Winsor-to-HLDN

Abstract

Formulation is an ancient concept, although the word has been used only recently. The first formulations made our civilization advance by inventing bronze, steel, and gunpowder; then, it was used in medieval alchemy. When chemistry became a science and with the golden age of organic synthesis, the second formulation period began. This made it possible to create new chemical species and new combinations “à la carte.” However, the research and developments were still carried out by trial and error. Finally, the third period of formulation history began after World War II, when the properties of a system were associated with its ingredients and the way they were assembled or combined. Therefore, the formulation and the systems’ phenomenology were related to the generation of some synergy to obtain a commercial product. Winsor’s formulation studies in the 1950s were enlightening for academy and industries that were studying empirically surfactant-oil-water (SOW) systems. One of its key characteristics was how the interfacial interaction of the adsorbed surfactant with oil and water phases could be equal by varying the physicochemical formulation of the system. Then, Hansen’s solubility parameter in the 1960s helped to reach a further understanding of the affinity of some substances to make them suitable to oil and water phases. In the 1970s, researchers such as Shinoda and Kunieda, and different groups working in Enhanced Oil Recovery (EOR), among them Schechter and Wade’s group at the University of Texas, made formulation become a science by using semiempirical correlations to attain specific characteristics in a system (e.g., low oil-water interfacial tension, formulation of a stable O/W or W/O emulsion, or high-performance solubilization in a bicontinuous microemulsion system at the so-called optimum formulation). Nowadays, over 40 years of studies with the hydrophilic-lipophilic deviation equation (HLD) have made it feasible for formulators to improve products in many different applications using surfactants to attain a target system using HLD in its original or its normalized form, i.e., HLDN. Thus, it can be said that there is still current progress being made towards an interdisciplinary applied science with numerical guidelines. In the present work, the state-of-the-art of formulation in multiphase systems containing two immiscible phases like oil and water, and therefore systems with heterogeneous or micro-heterogeneous interfaces, is discussed. Surfactants, from simple to complex or polymeric, are generally present in such systems to solve a wide variety of problems in many areas. Some significant cases are presented here as examples dealing with petroleum, foods, pharmaceutics, cosmetics, detergency, and other products occurring as dispersions, emulsions, or foams that we find in our everyday lives.

Microfluidic Study of Oil Droplet Stability in Produced Water with Combinations of Production Chemicals

“…When the CI is added, oil droplets are not created, which may indicate that the overall system is at the optimal HLD (equal to zero), with minimal emulsion stability (Figure ). Although the concentration of additives is not explicitly included as a variable in the general HLD equation, it has been shown that this is an important variable as well. − For the DE in the crude oil–water system, the coalescence frequency is largest at 2 ppm of DE. Apparently, this concentration of the DE corresponds to the stability minimum regime, with the HLD at around zero (Figure B).…”

Mesoscale Modeling of Micellization and Adsorption of Surfactants and Surfactant-Like Polymers in Solution: Challenges and Opportunities

“…For more details, see reviews by Salager and co-workers. [65][66][67]69 Another useful characteristic of a surfactant is the "packing parameter", also known as the "Israelachvili parameter". 72−76 The packing parameter, P, characterizes the most favorable micellar structure of a model surfactant in water (Figure 6).…”

“…More recently, the concept of HLB has been extended and refined via the introduction of the so-called HLD (hydrophilic–lipophilic difference) − (Figure ). The HLD analysis takes into account not only the nature of the surfactant but also the nature of the oil itself.…”

“…Thus, predicting HLD = 0 for a specific oil/water/surfactant system means that the surfactant is “perfectly balanced” between water and oil, so that one could obtain a thermodynamically stable cocontinuous emulsion or even a microemulsion. For more details, see reviews by Salager and co-workers. − , …”

Nanoparticles and essential oils with antiviral activity on packaging and surfaces: An overview of their selection and application

“…The presence of the surfactant or linker molecule allows a gradual polarity change at the vicinity of the interface (shell of the capsule), and thus more beneficial interactions between surfactant-aqueous phase and surfactantoil phase where solubilized EOs bioactive compounds are encountered (Chu et al, 2014;Salager et al, 2005Salager et al, , 2019. This allows the Winsor R relation (Bourrel & Schechter, 2010;Salager al., 2022;Winsor, 1954) to become R < 1 (i.e., hydrophiliclipophilic deviation, HLD N < 0) if an O/W emulsion is the target (Forgiarini et al, 2021;Salager et al, 2020). On the other hand, R = 1 or R slightly lower than 1, would be necessary if a bicontinuous microemulsion (HLD N = 0) or O/W microemulsion are needed, respectively (Ontiveros et al, 2013;Queste et al, 2007;Salager et al, 2020).…”