Structure and stability of microemulsion-based organo-gels

Abstract

The phase stability, structure and physical (mechanical) properties of gelatin-containing, AOT-stabilised microemulsion-based organo-gels have been studied as a function of their composition. Phase-stability studies indicate that the presence of small amounts of gelatin changes the shape and extent of the single-phase microemulsion region with respect to temperature. Small-angle neutron scattering shows that the gel structure is based on coexisting gelatin–water networks and microemulsion droplets. The gel structure is sensitive to the AOT and gelatin concentrations, water content, added salts and the nature of the oil used as the continuous phase. The likelihood of gel formation is linked to the proximity of the microemulsion upper-temperature phase boundary and the gelatin helix–coil transition temperature at ca. 32 °C. The frequency dependence of the elastic moduli of the organo-gels is similar to that of aqueous gelatin gels, being characteristic of a viscoelastic solid. The network strand density, derived from the relaxed elastic modulus, is consistent with the same parameter calculated from neutron scattering measurements.