Phase behavior and rheology of oil-swollen micellar cubic phase and gel emulsions in nonionic surfactant systems

Abstract

We have studied the phase behavior and rheological property of the cubic phase and related gel emulsions in water/nonionic/dodecane systems. In the phase behavior study, it is pointed out that the formation of the discontinuous cubic phase (I 1) is not common in all nonionic surfactant systems; however, a cubic phase (I 1) with oil-swollen micelles or a cubic phase microemulsion is found in the water/C 16EO 6/dodecane system, which can solubilize large amount of oil. It was also observed that water/C 16EO 6/dodecane system forms stable gel emulsion. In the rheological study we have found an anomalous behavior of the I 1 phase in the water/C 12EO 6/dodecane and the water/C 16EO 6/dodecane systems. In the water/C 12EO 6/dodecane system, the viscoelastic nature of the I 1 phase has been observed, which is shifted to the elastic nature with the addition of dodecane, whereas, highly elastic nature was observed in the water/C 16EO 6/dodecane system. In both the cases shear-thinning behavior were seen. The elastic modulus, G′ and complex viscosity, | η∗| of the I 1 phase increase with the dodecane concentration in the water/C 12EO 6/dodecane system, whereas, decreasing trend have been observed in the water/C 16EO 6/dodecane system. This anomalous behavior is suggested due to the nonspherical shape of micelles or polydispersity of the micelles in the water/C 16EO 6/dodecane system. The rheological behavior of the O/I 1 gel emulsion was also studied in both the systems.