Rubio Manuel, Sadek Samir, Vega Emilio José, Gañán-Calvo Alfonso Miguel, Montanero José María
Departamento de Ingeniería Mecánica, Energética y de los Materiales and Instituto de Computación Científica Avanzada (ICCAEx), Universidad de Extremadura, Avda. de Elvas s/n, E-06071 Badajoz, Spain.
Laboratory of Engineering for Energy and Environmental Sustainability, Department of Fluid Mechanics and Aerospace Engineering, University of Seville, E-41092 Seville, Spain.
Materials (Basel). 2021 Mar 8;14(5):1294. doi: 10.3390/ma14051294.
Long polymeric chains highly stretched and aligned with the flow confer a strong mechanical anisotropy on a viscoelastic solution. The electrically-driven transport of free ions under such conditions is far from being understood. In this paper, we determine experimentally whether the above-mentioned deviation from isotropy affects the electric charge transport across the liquid. To this end, we measure the electrical conductivity in the flow (stretching) direction of the cylindrical liquid filament formed in the elasto-capillary thinning that arises during the breakup of a viscoelastic liquid bridge. First, we examine the behavior of monodisperse solutions of polyethylene oxide (PEO) in a mixture of glycerine and water. For all the concentrations and molecular weights considered, the filament conductivity remains practically the same as the isotropic conductivity measured under hydrostatic conditions. However, we observe a decrease in the electric current at the end of elasto-capillary regime which may partially be attributed to the reduction of the liquid conductivity. Then, we measure the conductivity of bidisperse solutions of PEO with very different molecular weights. In this case, a significant decrease in conductivity is observed as the filament radius decreases. This constitutes the first experimental evidence of ion mobility reduction in stretching viscoelastic filaments, a relevant effect in applications such as electrospinning.
高度拉伸并与流动方向对齐的长聚合物链赋予粘弹性溶液很强的机械各向异性。在这种情况下，自由离子的电驱动输运远未被理解。在本文中，我们通过实验确定上述各向同性的偏差是否会影响液体中的电荷输运。为此，我们测量了在粘弹性液桥破裂过程中发生的弹性毛细管变细形成的圆柱形液体细丝在流动（拉伸）方向上的电导率。首先，我们研究了聚环氧乙烷（PEO）单分散溶液在甘油和水的混合物中的行为。对于所考虑的所有浓度和分子量，细丝电导率实际上与在静水条件下测量的各向同性电导率相同。然而，我们观察到在弹性毛细管状态结束时电流下降，这可能部分归因于液体电导率的降低。然后，我们测量了分子量差异很大的PEO双分散溶液的电导率。在这种情况下，随着细丝半径减小，观察到电导率显著下降。这构成了拉伸粘弹性细丝中离子迁移率降低的首个实验证据，这在诸如电纺等应用中是一个相关效应。
