Influence of Propylene Glycol on Aqueous Silica Dispersions and Particle-Stabilized Emulsions

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• 作者：Bernard P. Binks ; Paul D. I. Fletcher ; Michael A. Thompson ; Russell P. Elliott
• 刊名：Langmuir
• 出版年：2013
• 出版时间：May 14, 2013
• 年：2013
• 卷：29
• 期：19
• 页码：5723-5733
• 全文大小：639K
• 年卷期：v.29,no.19(May 14, 2013)
• ISSN：1520-5827

文摘

We have studied the influence of adding propylene glycol to both aqueous dispersions of fumed silica nanoparticles and emulsions of paraffin liquid and water stabilized by the same particles. In the absence of oil, aerating mixtures of aqueous propylene glycol and particles yields either stable dispersions, aqueous foams, climbing particle films, or liquid marbles depending on the glycol content and particle hydrophobicity. The presence of glycol in water promotes particles to behave as if they are more hydrophilic. Calculations of their contact angle at the air鈥揳queous propylene glycol surface are in agreement with these findings. In the presence of oil, particle-stabilized emulsions invert from water-in-oil to oil-in-water upon increasing either the inherent hydrophilicity of the particles or the glycol content in the aqueous phase. Stable multiple emulsions occur around phase inversion in systems of low glycol content, and completely stable, waterless oil-in-propylene glycol emulsions can also be prepared. Accounting for the surface energies at the respective interfaces allows estimation of the contact angle at the oil鈥損olar phase interface; reasonable agreement between measured and calculated phase inversion conditions is found assuming no glycol adsorption on particle surfaces.