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

Abstract

We have investigated the effects of glycerol on the formation and rheology of hexagonal phase (H(1)) and related O/H(1) gel emulsion in the water/C(12)EO(8)/dodecane system at 25 degrees C. It has been found that the aqueous solution of C(12)EO(8) forms H(1) phase, which could solubilize some amounts of dodecane. Beyond the solubilization limit, oil is separated and a two-phase region or H(1)+O phase appeared. Due to high viscosity of the H(1) phase, allows forming O/H(1) gel emulsion at the H(1)+O region. Rheological measurements (without glycerol) have shown that the rheogram of the H(1) phase does not change drastically with the addition of oil but the system is shifted to longer relaxation time. Simultaneously, the values of the absolute value(eta(*)) are found to increase with the addition of oil, which has been described with the neighboring micellar interaction. The rheogram of the O/H(1) 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 (H(1) phase). Addition of glycerol has brought an order-order transition or the microstructural transition from H(1)-lamellar (L(alpha)) phase, which is manifested from rheology and SAXS measurements. Viscosity of the O/H(1) 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 H(1) phase and dodecane). Structural parameters of the H(1) phase have been evaluated with the help of Bohlin's model and found that the coordination number of the H(1) phase depends not only the oil and glycerol concentrations but also temperature.

Phase Behavior, Formation, and Rheology of Cubic Phase and Related Gel Emulsion in Tween80/Water/Oil Systems

“…It is clearly shown that the values of |h*| steeply increase in the single I 1 phase with the squalane content and reach the highest value at the boundary point (~10 7 Pa s). This value is slightly lower than the reported value in other systems 15,24) . The value of G′ also increases in the I 1 phase and decreases in the I 1 +O or O/I 1 gel emulsion.…”

Influence of Surfactant Hydrophilicity on the Formation of Transparent O/I1-Type Emulsions

“…7 b. Similar results have been reported for the O/I 1 emulsion formed in the water/C 12 EO 8 / dodecane system with glycerol 8 .…”

Cosmetics’ Quality Control

“…Emulsions which exhibits G' values higher than G'' (Figure 14) are described as more stable than formulations with G'' values higher than G' (Figure 15), since they tends to recovery its initial structure faster and more efficiently than the others, and are less susceptible to the gravitational forces which retards or avoids the coalescence process and the phase separation of emulsions (Alam and Aramaki, 2009). So, the G' values higher than G'' in emulsions is a desirable feature, being an indicative of stability of the cosmetic system.…”