Sorbonne Université, Centre National de la Recherche Scientifique, UMR 7190, Institut Jean Le Rond d'Alembert , F-75005 Paris , France.
Département de Physique, École Normale Supérieure, CNRS, PSL Research University , F-75005 Paris , France.
Langmuir. 2018 Oct 16;34(41):12244-12250. doi: 10.1021/acs.langmuir.8b02128. Epub 2018 Oct 3.
Silicone elastomers such as polydimethylsiloxane (PDMS) are convenient materials routinely used in laboratories that combine ease of preparation, flexibility, transparency, and gas permeability. However, these elastomers are known to contain a small fraction of uncrosslinked low-molecular-weight oligomers, the effects of which are not completely understood, particularly when used in contact with liquids. Here, we show that triple lines involving air, water, and PDMS elastomers are responsible for the contamination of water-air interfaces by uncrosslinked silicone oligomers through a capillarity-induced extraction mechanism. We investigate both the case of static and moving contact lines and study various geometries ranging from partially immersed PDMS plates to water droplets or air bubbles deposited on PDMS plates, all involving air-water-elastomer triple lines. We demonstrate experimentally that the contamination timescale is strikingly shorter for moving contact lines than in the static case. Eventually, we propose a simple poroelastic model capturing the main features of contamination observed in experiments.
硅橡胶弹性体（如聚二甲基硅氧烷（PDMS））是实验室中常用的方便材料，具有易于制备、柔韧性、透明度和透气性等优点。然而，这些弹性体已知含有少量未交联的低分子量低聚物，其影响尚不完全清楚，特别是在与液体接触时。在这里，我们表明，空气、水和 PDMS 弹性体之间的三线接触导致未交联的硅氧烷低聚物通过毛细作用诱导提取机制污染水-空气界面。我们研究了静态和动态接触线的情况，并研究了各种几何形状，从部分浸入 PDMS 板到沉积在 PDMS 板上的水滴或气泡，所有这些都涉及空气-水-弹性体三线接触。我们通过实验证明，与静态情况相比，动态接触线的污染时间明显更短。最终，我们提出了一个简单的多孔弹性模型，该模型捕捉了实验中观察到的污染的主要特征。
