Center for Single Particle Science and Engineering, (SPSE), Department of Molecular Medicine, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark.
Center for Single Particle Science and Engineering, (SPSE), Department of Molecular Medicine, University of Southern Denmark, Campusvej 55, DK-5230 Odense, Denmark.
J Colloid Interface Sci. 2017 Oct 15;504:765-779. doi: 10.1016/j.jcis.2017.05.077. Epub 2017 May 25.
The dynamic adsorption of ionic surfactants at air-water interfaces have been less-well studied than that of the simpler non-ionics since experimental limitations on dynamic surface tension (DST) measurements create inconsistencies in their kinetic analysis. Using our newly designed "Micropipette interfacial area-expansion method", we have measured and evaluated both equilibrium and dynamic adsorption of a well-known anionic surfactant, sodium dodecyl sulphate (SDS), in the absence or presence of 100mM NaCl. Our focus was to determine if and to what extent the inclusion of a new correction parameter for the "ideal ionic activity", A, can renormalize both equilibrium and dynamic surface tension measurements and provide better estimates of the diffusion coefficient of ionic surfactants in aqueous media obtained from electroneutral models, namely extended Frumkin isotherm and Ward-Tordai adsorption models. We found that the estimated value of the new parameter, A=0.29, is key to obtain the diffusion coefficient D=5.3±0.3×10cm/s for SDS, in excellent agreement with the literature. These new technique and analyses can now be applied to study the interfacial adsorption of a range of both ionic and non-ionic surface-active molecules, including the potentially slower-diffusing polymers and biological materials like lipids, peptides, and proteins.
与简单的非离子型表面活性剂相比，离子型表面活性剂在气-液界面的动态吸附研究较少，这是因为动态表面张力（DST）测量的实验限制导致其动力学分析存在不一致性。我们使用新设计的“微管界面面积扩展法”，测量并评估了在不存在或存在 100mM NaCl 的情况下，一种已知的阴离子表面活性剂十二烷基硫酸钠（SDS）的平衡和动态吸附。我们的重点是确定是否以及在何种程度上，包含一个新的理想离子活度“A”校正参数可以使平衡和动态表面张力测量正常化，并从电中性模型（即扩展 Frumkin 等温线和 Ward-Tordai 吸附模型）提供更好的估计值，即离子型表面活性剂在水介质中的扩散系数。我们发现，新参数 A=0.29 的估计值是获得 SDS 扩散系数 D=5.3±0.3×10cm/s 的关键，这与文献值非常吻合。现在，这些新技术和分析方法可以应用于研究一系列离子型和非离子型表面活性剂的界面吸附，包括潜在扩散速度较慢的聚合物以及生物材料，如脂质、肽和蛋白质。
