Rheological behavior of polyoxyethylene phytosterol-polyoxyethylene cholesterol/tetraethylene glycol monododecyl ether/water systems.

We have studied the rheological properties of mixtures of polyoxyethylene (10 mol) phytosterol (PhyEO(10)) and polyoxyethylene (10 mol) cholesterol (ChEO(10)) mixed in different ratios along with tetraethylene glycol monododecyl ether (C(12)EO(4)) surfactants in water. Addition of C(12)EO(4) to the aqueous solution of a mixture of (PhyEO(10) + ChEO(10)) 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 C(12)EO(4) concentration and relaxation time (tau(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.