Coacervate Studies of Non-Sulfate Shampoos

Abstract

Shampoos typically consist of cationic polymers, anionic surfactants, and amphoteric surfactants as their primary components. During use, when these formulations are diluted with water, they often undergo liquid-liquid phase separation, resulting in the formation of a dilute phase and a concentrated phase. This concentrated phase, known as coacervate, is rich in polymers and surfactants and plays a significant role in determining the sensory characteristics and overall user experience of shampoos. The quantity and quality of the coacervate are widely acknowledged to influence the foaming, spreading, and conditioning properties of shampoo. Traditionally, shampoos have relied on sulfate-based anionic surfactants. However, there has been a growing shift towards non-sulfate formulations due to consumer demand for milder and potentially less irritating alternatives. Despite this trend, studies examining coacervation phenomena in non-sulfate shampoos remain limited. In this study, we analyzed four commercially available non-sulfate shampoos to investigate the relationship between coacervate properties̶such as formation region, quantity, particle size, ζ-potential, and viscoelasticity̶and the perceived user experience. Our findings reveal that the characteristics of the coacervate from non-sulfate shampoos significantly influence the sensory attributes of formulas, including foaming, sliminess, quickness of rinsing, and smoothness at rising and drying. This study highlights the importance of understanding coacervate behavior in the formulation of non-sulfate shampoos to optimize user satisfaction. Further research into the interplay between formulation ingredients and coacervate properties could provide valuable insights for the development of next-generation shampoos.