Glycerol effects on the formation and rheology of cubic phase and related gel emulsion

We have investigated the effects of glycerol on the formation and rheological behavior of cubic phase (I1) and related O/I1 gel emulsion in a water/C12EO8/dodecane system at 25 °C. The phase behavior of the water/C12EO8/dodecane system was studied by optical observation and structures of different liquid crystalline phases were identified by small-angle X-ray scattering (SAXS) techniques. Addition of dodecane (2 wt%) to aqueous solutions of C12EO8 in a concentrated region (40 wt%) leads to the formation of the I1 phase (which was absent without the addition of oil). The I1 phase solubilized some amount of oil and at higher oil concentrations the I1 + O phase was formed, allowing the preparation of O/I1 gel emulsion. Rheological measurements have shown that the complex viscosity, |η∗||η∗|, of the I1 phase is tremendously high (∼107 Pas) and it increases with increasing oil concentration, attains a maximum value near the phase boundary, and then decreases drastically in the I1 + O region. The increasing |η∗||η∗| or decreasing tanδ(G″/G′)tanδ(G″/G′) can be ascribed with the interactions among the neighboring micelles. The decreasing trend of the |η∗||η∗| in the I1 + O region is simply due to the low volume fraction of the I1 phase. It has been shown that glycerol decreases the viscosity of the I1 phase and related gel emulsion, which is due to the I1–hexagonal phase (H1) microstructural transition. Digital images show the physical appearance of the emulsion, which depends on the glycerol concentration changes from translucent to transparent.

The addition of glycerol changes the rheological behavior of the micellar cubic phase (I1) causing a transition from elastic to viscoelastic behavior.Figure optionsDownload as PowerPoint slide