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

We have investigated the effects of glycerol on the formation and rheology of hexagonal phase (H1) and related O/H1 gel emulsion in the water/C12EO8/dodecane system at 25 °C. It has been found that the aqueous solution of C12EO8 forms H1 phase, which could solubilize some amounts of dodecane. Beyond the solubilization limit, oil is separated and a two-phase region or H1 + O phase appeared. Due to high viscosity of the H1 phase, allows forming O/H1 gel emulsion at the H1 + O region. Rheological measurements (without glycerol) have shown that the rheogram of the H1 phase does not change drastically with the addition of oil but the system is shifted to longer relaxation time. Simultaneously, the values of the ∣η*∣ are found to increase with the addition of oil, which has been described with the neighboring micellar interaction. The rheogram of the O/H1 gel emulsion shows gel type nature (G′ > G″) but the viscosity monotonically decreases with increasing oil content, which could be due to the lower volume fraction of the continuous phase (H1 phase). Addition of glycerol has brought an order–order transition or the microstructural transition from H1-lamellar (Lα) phase, which is manifested from rheology and SAXS measurements. Viscosity of the O/H1 gel emulsion also decreases with increasing glycerol content. Digital images show the physical appearance of the gel emulsion changes from turbid to transparent, which is depended on the glycerol concentration (since glycerol matches the refractive index of the H1 phase and dodecane). Structural parameters of the H1 phase have been evaluated with the help of Bohlin’s model and found that the coordination number of the H1 phase depends not only the oil and glycerol concentrations but also temperature.

Addition of glycerol changes the rheological behavior of the hexagonal phase (H1) causing an order–order transition from H1 phase to lamellar (Lα) phase.Figure optionsDownload as PowerPoint slide