title: Effect of molecular weight of triglycerides on the formation and rheological behavior of cubic and hexagonal phase based gel emulsions.
abstract: The effect of triglyceride molecular weight on the formation and rheology of cubic (O/I(1)) and hexagonal (O/H(1)) phase based gel emulsions has been studied in water/C(12)EO(8) systems. It was found that the addition of TDG (1,2,3-tridecanoyl glycerol) in the micellar solution leads to the formation of the I(1) phase, which can solubilize some added oil. From SAXS data, it is revealed that the interlayer spacing (d) and the length of hydrophobic part (r(I)) increase with increasing TDG concentration in the I(1) phase, whereas the effective cross-sectional area (a(s)) decreases. After the oil solubilization limit, the d value remains nearly constant, indicating the I(1)+O phase appears. The high viscosity of the I(1) phase facilitates the formation of the O/I(1) gel emulsion. It has been observed that the formation and stability of the O/I(1) and O/H(1) gel emulsion is highly dependent on the molecular weight of triglycerides, namely, the high molecular weight triglycerides show better performance (formation and stability) compared to the low molecular weight triglycerides. The rheological behavior of the I(1) phase was found to change from viscoelastic to elastic nature with TDG content. The values of the complex viscosity, mid absolute value(eta*) show different trends at different fixed frequencies within the I(1) phase, whereas it decrease monotonically in the O/I(1) gel emulsions. The increasing values of the absolute value(eta*) (at lower frequency) could be due to the neighboring micellar interaction and decreasing values of the absolute value(eta*) in the O/I(1) gel emulsion could relate to the volume fraction of the I(1) phase in the system. It is also figured out that the rheological parameters (elastic modulus, viscous modulus, and absolute value(eta*)) of the O/I(1) the gel emulsion do not depend on the oil nature, whereas the O/H(1) gel emulsion shows oil nature dependency.
authors.affiliation: Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya-ku, Yokohama 240-8501, Japan.
authors.forename: Mohammad Mydul
authors.initials: MM
authors.lastname: Alam
authors.forename: Kenji
authors.initials: K
authors.lastname: Aramaki