Design of Viscoelastic Surfactant-oil-water Structures with the Hydrophilic-lipophilic Difference (HLD) and Net-average Curvature (NAC) Frameworks
Manipulating the self-assembly of surfactants into viscoelastic structures such as wormlike micelles and liquid crystals is an important aspect in the development of personal care products and nanostructured materials. Central to this is the curvature of the surfactant membrane, which is one of the governing concepts of surfactant self-assembly. It can be altered with multiple parameters including differences in surfactant molecular structure, added salts, added oils, and temperature. Current frameworks used to guide the design of formulations such as the packing factor do not excel at predicting the necessary combination required to produce the desired structure. A new approach presented in this work relates the formation of viscoelastic structures including wormlike micelles and liquid crystals to curvature-related phase inversion phenomena observed in surfactant-oil-water systems. The phase inversion point, in turn, can be predicted with the hydrophilic-lipophilic difference (HLD) framework. This approach was successful at predicting the formation of viscoelastic fluids for extended anionic surfactants, and a model anionic surfactant, sodium dihexyl sulfosuccinate for a variety of salinities and polar/non-polar oils at low surfactant and oil contents (
liquid crystals, micelles, microemulsion, rheology, surfactant
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