Increased Ordering of Potassium Stearate/Stearic Acid/Glyceryl\nStearate Confined between Swollen Cross-Linked Poly(acrylic acid)

In\nthis paper, we investigate the phase behavior of a surfactant\nmixture comprising glyceryl stearate, potassium stearate, and stearic\nacid, in the presence of Carbopol, a commonly used thickener in personal\ncare products. At low Carbopol concentrations (<0.03%), the surfactant\nmixture interacted with Carbopol electrostatically, increasing the\ndegree of Carbopol swelling and, consequently, the overall viscosity.\nHowever, such an effect diminished as the Carbopol concentration was\nfurther increased. At a Carbopol concentration of 0.2%, two types\nof liquid crystalline surfactant structures, namely, multilamellar\nvesicles and lamellae, were observed between the swollen Carbopol\ndomains. Although similar types of surfactant structures were present\nin a much more concentrated surfactant solution having a similar viscosity\nbut without Carbopol, the lamellae in the presence of Carbopol were\nmore ordered and with a larger <i>d</i> spacing. The increased\nordering was probably induced by the interactions between the surfactants\nand Carbopol as the surfactants were confined between the swollen\nCarbopol domains.