Microstructure of colloidal liquid aphrons (CLAs) by freeze fracture transmission electron microscopy (FF-TEM)

Abstract

Colloidal liquid aphrons (CLAs) composed of triethylene glycol monododecyl ether (C 12E 3)/ n-decane/sodium dodecyl sulphate (SDS) or Tween 80/water have been visualized by freeze fracture transmission electron microscopy (FF-TEM) and confirmed by small angle X-ray scattering (SAXS) and polarizing microscopy. The resolution achieved allows detailed inspection of the size, shape of individual micelles, as well as core-shell structure of CLAs. The microstructure of CLAs was compared with that conventional emulsions presented, particularly high internal phase ratio emulsions (HIPREs), from the viewpoint of morphology. The combined results indicate that the CLAs consist of spherical, oil droplets (oil-rich phase) of micron size separated by an aqueous “soapy shell” (water-rich phase) and there exist supramolecular structures such as reversed micelles and O/W micelles or microemulsions in oil-rich and water-rich phases, respectively. The total interfacial area of stable CLAs is consistent with that of colloidal gas aphrons (CGAs) reported previously, with an approximate thickness of 0.3–0.4 μm. It has been shown throughout this work that the overall microstructure CLAs presented here is somewhat analogous to that of HIPREs, with biphasic structure and presence of the supramolecular aggregates in these phases, which seems to support the Princen's opinion.