Shampoo and Conditioner Science 94 ions bind, hydrophobic interaction between the hydrophobic surfactant tails causes the polymer-surfactant complex to phase separate at concentrations below the surfactant critical micelle concentration. Above the CMC, the surfactant concentration is sufficiently high to form micelles or hemi-micelles along the polyion chain and the polyion/surfactant complex is solubilized. Conditioning shampoos are formulated within the range of surfactant concentrations that correspond to this solubilized regime. When these shampoos are diluted to a concentration that is in the vicinity of the CMC, then the complex coacervate phase-separates. The separated phase is deposited on the hair during rinsing and it can co-deposit other additives such as silicone conditioning agents or anti-dandruff agents. Maximum coacervate deposition occurs at precise ratios of cationic polymer to anionic surfactant, but the optimum ratio for coacervation might not coincide with the best ratios for cleaning and foaming. Cationic guar has been a known additive for 2-in-1 shampoos for more than three decades. However, it has now been shown that improved post-shampoo detangling times are achieved by including Figure 16. A schematic phase diagram that explains the mechanism of coacervate formation in 2-in-1 shampoos