Self assembly in aqueous and non-aqueous sugar-oil mixtures.

摘要

In aqueous systems, the hydrophobic effect drives the self-assembly of amphiphiles into a broad range of micellar, rod-like, bicontinuous, and liquid-crystalline complex fluids, which have myriad biological, materials, and product applications. However, amphiphilic self-assembly is not limited to aqueous systems. We have explored the self-assembly of surfactants in anhydrous sugars. Our study reveals that anhydrous powders of sugars and surfactants suspended in oil spontaneously form molten microemulsion glasses with nanometer-size domains of sugar and liquid oil without mixing. The low cost, water solubility, low toxicity and stabilizing properties of glassy sugars make them ideal water replacements for many pharmaceutical, food and materials synthesis applications. The optical clarity and solid appearance of these glasses at room temperature belie their inclusion of more than 50% (vol.) oil, which confers liquid-like diffusivity.;We have also investigated the phase behavior and characterization studies of edible microemulsions of d-limonene (orange oil) with concentrated sugar solutions (>65 wt%) using sucrose laurate and sucrose oleate as surfactants. The phase behavior of these mixtures is studied as a function of temperature and surfactant composition, identifying the specific effects of sugar concentration, surfactant chain length, and oil loading on the formation of microemulsion and lamellar phases. Small-angle neutron scattering experiments confirm the presence of well-structured microemulsions with domain sizes ranging from ∼35 to 60 nm. With few exceptions, the patterns of microemulsion phase behavior with concentrated sugar solutions are very similar to that of aqueous systems. These studies simulate the effect of either increasing sugar concentrations or removing water (e.g. spray drying) on the one phase microemulsion region. In addition to providing better understanding of the underlying phenomena of formation of sugar based microemulsion glasses, these aqueous sugar based microemulsions have potential applications in encapsulation of hydrophobic and hydrophilic actives, which are used in food, pharmaceuticals and many other industries.