Rheological Behavior of Polyoxyethylene Phytosterol-Polyoxyethylene Cholesterol/Tetraethylene Glycol Monododecyl Ether/Water Systems

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We have studied the rheological properties of mixtures of polyoxyethylene (10 mol) phytosterol (PhyEO₁₀) and polyoxyethylene (10 mol) cholesterol (ChEO₁₀) mixed in different ratios along with tetraethylene glycol monododecyl ether (C₁₂EO₄) surfactants in water. Addition of C₁₂EO₄ to the aqueous solution of a mixture of (PhyEO₁₀ + ChEO₁₀) results in one-dimensional micellar growth and formation of viscoelastic solution of entangled wormlike micelles. Steady-shear rheological measurements show the Newtonian flow behavior at low shear-rate region and non-Newtonian flow behavior at higher shear-rate for viscous samples. The dynamic rheological data of the viscoelastic samples indicate the plateau modulus (G_o) increases monotonically with C₁₂EO₄ concentration and relaxation time (τ_R) display a maximum at a composition corresponding to the viscosity maximum. The prepared viscoelastic sample in mixed nonionic surfactant systems has potential applications in cosmetic formulation.