The lamellar-to-vesicle phase transition by shear experiments

It is shown that the transformation of an L-3-phase to an ionically charged L-alpha-phase with stacked bilayers can be induced by the hydrolysis reaction of an ester. This process takes place on a time scale of minutes with ethyloxalate as an ester and occurs spontaneously. If this low-viscous L-alpha-phase is subjected to shear it is transformed into a highly viscous vesicle phase (onion phase). The structural changes during this transformation process have been monitored by conductivity, rheology and small angle neutron scattering (SANS) experiments. We observed that the transformation occurs in several steps. For low shear rates the transformation time tau decreases Linearly with the shear rate (tau gamma = constant 2000) while for higher shear rates a different mechanisms occurs.