Champougny Lorène, Scheid Benoit, Restagno Frédéric, Vermant Jan, Rio Emmanuelle
Laboratoire de Physique des Solides, CNRS & Université Paris-Sud, 91405 Orsay Cedex, France.
Soft Matter. 2015 Apr 14;11(14):2758-70. doi: 10.1039/c4sm02661f.
The behavior of thin liquid films is known to be strongly affected by the presence of surfactants at the interfaces. The detailed mechanism by which the latter enhance film stability is still a matter of debate, in particular concerning the influence of surface elastic effects on the hydrodynamic boundary condition at the liquid/air interfaces. In the present work, "twin" hydrodynamic models neglecting surfactant transport to the interfaces are proposed to describe the coating of films onto a solid plate (Landau-Levich-Derjaguin configuration) as well as soap film pulling (Frankel configuration). Experimental data on the entrained film thickness in both configurations can be fitted very well using a single value of the surface elasticity, which is in good agreement with independent measurements by mean of surface expansion experiments in a Langmuir through. The analysis thus shows that soap films or dip coating experiments may be used to measure the surface elasticity of surfactant solutions in the insoluble limit, namely as long as the film generation dynamics is fast compared to the surfactant adsorption timescale.
众所周知，界面处表面活性剂的存在会强烈影响薄液膜的行为。表面活性剂增强膜稳定性的详细机制仍是一个有争议的问题，特别是关于表面弹性效应在液/气界面处对流体动力学边界条件的影响。在本工作中，提出了忽略表面活性剂向界面传输的“孪生”流体动力学模型，以描述在固体板上的液膜涂覆（朗道-列维奇-杰加金构型）以及皂膜拉伸（弗兰克尔构型）。使用单一表面弹性值可以很好地拟合这两种构型中夹带液膜厚度的实验数据，这与在朗缪尔槽中通过表面膨胀实验进行的独立测量结果非常吻合。因此分析表明，皂膜或浸涂实验可用于测量不溶性极限下表面活性剂溶液的表面弹性，即只要膜生成动力学比表面活性剂吸附时间尺度快。
