Lecithin organogel with new rheological and scaling behavior

It was established from an experimental study on a lecithin organogel in n-decane performed by means of an oscillatory rheology that frequency dependencies for complex viscosity and storage modulus have intermediate plateaus at certain molar ratios of water to lecithin. This type of rheological behavior was previously observed for blends of homopolymers which differ significantly in their molecular weight. To mathematically describe the experimental data, a Maxwell model including two relaxation processes (i.e., two elements in parallel) was considered. Both relaxation modes were constrained according to the known interrelation between terminal relaxation time, zero-shear viscosity, and plateau modulus. The experimental results were in good agreement with the model considered. By applying a fitting procedure, two sets of values for relaxation time, zero-shear viscosity and plateau modulus, were obtained for each of the relaxation processes. When the scaling behavior was examined, a disagreement with current models for the polymer-like micelles was found. The presented results lead to a suggestion that the lecithin organogel at increased water-to-lecithin molar ratios has more complicated structural organization than that observed for surfactant based micellar aggregates before.