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 react ion of an ester. This process takes place on a time scale of minutes with e thyloxalate as an ester and occurs spontaneously. If this low-viscous L-alp ha-phase is subjected to shear it is transformed into a highly viscous vesi cle phase (onion phase). The structural changes during this transformation process have been monitored by conductivity, rheology and small angle neutr on scattering (SANS) experiments. We observed that the transformation occur s in several steps. For low shear rates the transformation time tau decreas es Linearly with the shear rate (tau gamma = constant 2000) while for highe r shear rates a different mechanisms occurs.