Diffusiophoretic mobility of charge‐regulating porous particles
Diffusiophoretic mobility of charge‐regulating porous particles
复制标题
电荷调节多孔颗粒的扩散电泳迁移率
作者：
W. C. Li;H. Keh
首次对具有任意厚度双电层的电荷调节多孔球（例如聚电解质线圈）在浓度梯度规定的电解质溶液中的扩散电泳进行了分析研究。离子官能团和流体动力摩擦链段均匀分布在可渗透颗粒内，并且官能团缔合和解离反应的电荷调节模型将固定电荷密度与局部电势联系起来。控制电势、离子电化学势和流体速度分布的动电方程被求解为基本固定电荷密度的幂级数展开式。从力平衡导出了粒子扩散电泳迁移率的明确公式，该粒子在等电点处消失。电荷调节对扩散电泳迁移率的影响是重要且有趣的，这取决于各种颗粒和电解质特性，例如离子官能团的反应平衡常数。电荷决定离子的总体浓度的变化可以在扩散电泳速度方向上产生不止一种反转。获得的结果与不可渗透颗粒的结果明显不同，并为实验数据的解释提供了有价值的信息。
The diffusiophoresis of a charge‐regulating porous sphere, such as polyelectrolyte coil, with an arbitrary thickness of the electric double layer in an electrolyte solution prescribed with a concentration gradient is analytically studied for the first time. The ionogenic functional groups and hydrodynamic frictional segments distribute uniformly within the permeable particle, and a charge regulation model for the association and dissociation reactions of the functional groups relates the fixed charge density to the local electric potential. The electrokinetic equations governing the electric potential, ionic electrochemical potential, and fluid velocity distributions are solved as power‐series expansions in the basic fixed charge density. An explicit formula for the diffusiophoretic mobility of the particle, which vanishes at the isoelectric point, is derived from a force balance. The effects of charge regulation on the diffusiophoretic mobility, which depend on various particle and electrolyte characteristics such as the reaction equilibrium constants of the ionogenic functional groups, are significant and interesting. The variation in the bulk concentration of the charge‐determining ions can produce more than one reversal in the direction of the diffusiophoretic velocity. The obtained results differ conspicuously from those of impermeable particles and provide valuable information for the interpretation of experimental data.