The role of the surfactant head group in the emulsification process: Binary (nonionic–ionic) surfactant mixtures

详细信息	查看全文 | 推荐本文 |

• 作者：T.P. Goloub and R.J. Pugh
• 关键词：Binary surfactant mixtures ; Surfactant head groups ; Emulsification ; Emulsifier droplet size ; Nonionic/ionic surfactants
• 刊名：Journal of Colloid and Interface Science
• 出版年：2005
• 期刊代码：125_00219797
• 类别：ch
• 出版时间：2005
• 卷：291
• 期：1
• 页码：256-262
• 文件大小：358 K

摘要

Dilute emulsions of dodecane in water were prepared under constant flow rate conditions with binary surfactant systems. The droplet size distribution was measured as a function of the mixed surfactant composition in solution. The systems studied were (a) the mixture of anionic sodium dodecyl sulfate (SDS) with nonionic hexa(ethyleneglycol) mono n-dodecylether (C₁₂E₆) and (b) the mixture of cationic dodecyl pyridinium chloride (DPC) with C₁₂E₆. At a constant concentration of SDS or DPC surfactant in solution (below the CMC) the mean emulsion droplet size decreases with the increase in the amount of C₁₂E₆ added to the solution. However, a sharp break of this droplet size occurs at a critical concentration and beyond this point the mean droplet size did not significantly change upon further increase of the C₁₂E₆. This point was found to corresponded to the CMC of the mixed surfactant systems (as previously determined from microcalorimetry measurements) and this result suggested the mixed adsorption layer on the emulsion droplet was similar to the surfactant composition on the mixed micelles. The emulsion droplet size as a function of composition at the interface was also studied. The mean emulsion droplet size in SDS–C₁₂E₆ solution was found to be lower than that in DPC–C₁₂E₆ system at the equivalent mole fraction of ionic surfactant at interface. This was explained by the stronger interactions between sulphate and polyoxyethylene head groups at the interface, which facilitate the droplet break-up. Counterion binding parameter (β) was also determined from zeta-potential of dodecane droplets under the same conditions and it was found that (β) was independent of the type of the head group and the mole fraction of ionic surfactant at interface.