Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de paris, 4 place Jussieu, 75005 Paris, France.
Soft Matter. 2017 Oct 4;13(38):6816-6830. doi: 10.1039/c6sm02191c.
Liquid foams are unstable due to aging processes such as drainage, coalescence or coarsening. Since these processes modify the foam structure, they can be a severe limitation to the elaboration of solid foams with controlled structures inherited from their liquid precursors. Such applications call for a thorough understanding of foam stabilization. Here we study how coarsening can be inhibited by the combined effects of a mixture of gas containing a species insoluble in the foaming solution and of gelation of the foaming solution. We present experiments with model ordered liquid foams and hydrogel foams. They allow us to identify the underlying physical mechanisms of stabilization and their governing parameters, namely the bubble radius R, the foam shear modulus G and the number η of insoluble trapped gas molecules per bubble. We propose a scaling model that predicts the stability diagram of an ideal monodisperse perfectly ordered foam as a function of R, G and η, in qualitative agreement with our data. We show that the domain of stable foams is governed by a characteristic elasto-capillary radius set by the ratio of surface tension to storage modulus.
由于老化过程（如排液、聚结或粗化），液体泡沫是不稳定的。由于这些过程改变了泡沫结构，它们可能严重限制了具有从其液体前体继承的受控结构的固体泡沫的制备。此类应用需要深入了解泡沫稳定性。在这里，我们研究了通过包含在发泡溶液中不溶的物质的气体混合物的组合效应以及发泡溶液的胶凝作用如何抑制粗化。我们进行了具有模型有序液体泡沫和水凝胶泡沫的实验。它们使我们能够确定稳定的基本物理机制及其控制参数，即气泡半径 R、泡沫剪切模量 G 和每个气泡中不溶性捕获气体分子的数量 η。我们提出了一个标度模型，该模型预测了理想单分散完全有序泡沫的稳定图作为 R、G 和 η 的函数，与我们的数据定性一致。我们表明，稳定泡沫的区域由由表面张力与储能模量的比值设定的特征弹性毛细半径控制。
