Direct Measurement of Contact Angles of Silica Particles in Relation to Double Inversion of Pickering Emulsions

作者：Binks Bernard Paul^*; Isa Lucio; Tyowua Andrew Terhemen

来源：Langmuir, 2013, 29(16): 4923-4927.

DOI：10.1021/la4006899

In an alkane-water system containing submicrometer silica particles at high pH, double emulsion inversion from oil-in-water (o/w) to water-in-oil (w/o) to oil-in-water can be effected by increasing the concentration of a dichain cationic surfactant in water. The contact angle theta of the particles at the planar oil-water interface has been measured directly using freeze-fracture shadow-casting cryo-scanning electron microscopy, enabling single-particle measurements of high accuracy. theta passes through a maximum with respect to surfactant concentration. It is shown that particles undergo a hydrophilic-hydrophobic-hydrophilic transition corresponding closely to the o/w-w/o-o/w transformation observed in emulsions. These results unequivocally link the single-particle contact angles to the type of particle-stabilized emulsion, confirming macroscopic emulsion inversion on the microscopic level.

• 出版日期2013-4-23