Mohlin Kristina, Holmberg Krister
Department of Chemical and Biological Engineering, Applied Surface Chemistry, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
J Colloid Interface Sci. 2006 Jul 1;299(1):435-42. doi: 10.1016/j.jcis.2006.02.007. Epub 2006 Feb 28.
Acid labile surfactants containing an ortho ester link are used as emulsifiers for an aliphatic oil, squalane. The emulsions were made in the presence of a cationic polymer, either polyamine or the corresponding hydrophobically modified polyamine. Spontaneous hydrolysis of the surfactant resulted in emulsions stabilized by polymer together with degradation products from the surfactant. The effect of breakdown of the surfactant on the emulsion was evaluated by means of droplet size measurements and kinetic stability. One linear and one branched nonionic ortho ester surfactant with the same number of oxyethylene units were characterized and used for the purpose. The ortho ester surfactants are complex mixtures of components, ranging from very hydrophilic to very hydrophobic species. The chemical shift of the central methine proton in the ortho ester link is extremely sensitive to the substitution pattern and it was possible to identify by (1)H NMR the components that make up the surfactants, as has been reported earlier. The change in emulsion stability, the change in droplet size and the rate of surfactant hydrolysis were studied at acidic pH at room temperature. Both gas chromatography and (1)H NMR were used in order to monitor the surfactant degradation. The presence of a polymer gave a more sluggish breakdown of the surfactants, probably due to hydrophobic shielding by the polymer. There was a good correlation between increase of droplet size and degree of surfactant decomposition.
含有原酸酯键的酸不稳定表面活性剂被用作脂肪油角鲨烷的乳化剂。乳液是在阳离子聚合物（多胺或相应的疏水改性多胺）存在下制备的。表面活性剂的自发水解导致乳液由聚合物以及表面活性剂的降解产物稳定。通过液滴尺寸测量和动力学稳定性评估表面活性剂分解对乳液的影响。为此表征并使用了具有相同氧化乙烯单元数的一种线性和一种支链非离子原酸酯表面活性剂。原酸酯表面活性剂是成分的复杂混合物，范围从非常亲水到非常疏水的物质。原酸酯键中中心次甲基质子的化学位移对取代模式极其敏感，并且如先前报道的那样，可以通过¹H NMR鉴定构成表面活性剂的成分。在室温下在酸性pH条件下研究了乳液稳定性的变化、液滴尺寸的变化和表面活性剂水解速率。使用气相色谱法和¹H NMR来监测表面活性剂的降解。聚合物的存在使表面活性剂的分解更缓慢，这可能是由于聚合物的疏水屏蔽作用。液滴尺寸的增加与表面活性剂分解程度之间存在良好的相关性。
