E2S UPPA, CNRS, TotalEnergies, LFCR UMR5150, Universite de Pau et des Pays de l'Adour, Anglet, France.
Centre National d'Études Spatiales (CNES), 2, Place Maurice Quentin, Paris, France.
Eur Phys J E Soft Matter. 2022 May 28;45(6):52. doi: 10.1140/epje/s10189-022-00202-5.
We performed ground-based experiments on the sample polystyrene-toluene-cyclohexane in order to complement the experimental activities in microgravity conditions related to the ESA projects DCMIX4 and Giant Fluctuations. After applying a stabilizing thermal gradient by heating from above a layer of the fluid mixture, we studied over many hours the density variations in the bidimensional horizontal field by means of a Shadowgraph optical setup. The resulting images evidence the appearance of convective instability after a diffusive time associated with the binary molecular solvent consisting of toluene and cyclohexane, confirming the negative sign of the Soret coefficient of this mixture. After a larger diffusive time related to mass diffusion of the polystyrene in the binary solvent, convection was suppressed by the increasing stabilizing density gradient originated by the Soret-induced concentration gradient of the polymer. This is compatible with a positive sign of the Soret coefficient of the polymer in the binary solvent.
我们在聚苯乙烯-甲苯-环己烷样品上进行了地面实验，以补充与 ESA 项目 DCMIX4 和 Giant Fluctuations 相关的微重力条件下的实验活动。在通过从上方加热一层流体混合物施加稳定的热梯度之后，我们使用阴影图形光学装置在多个小时内研究了二维水平场中的密度变化。所得图像表明，在与由甲苯和环己烷组成的二元分子溶剂相关的扩散时间之后出现了对流不稳定性，这证实了该混合物的 Soret 系数为负。在与聚苯乙烯在二元溶剂中扩散相关的更大扩散时间之后，对流被由聚合物的 Soret 诱导的浓度梯度引起的稳定密度梯度的增加所抑制。这与聚合物在二元溶剂中的 Soret 系数为正相符。
