Electrokinetics of Soft Matter: Diffusiophoresis and Charge-Regulation Phenomena
Date Issued
2015
Date
2015
Author(s)
Fang, Hsuan
Abstract
The electrokinetic behavior of soft matter including polyelectrolytes amd polymer gels is investigated, with consideration of charge-regulation phenomena. A pseudo-spectral method based on Chebyshev polynomials is used to solve the resulted general electrokinetic equations. We found, among other things, that the higher the particle surface potential or the fixed charge density of the polymer layer of the polyelectrolyte, the more serious distortion of the ion clouds, which generates an induced electric field opposite to the particle motion, thus reducing the particle mobility, as an effect referred to the polarization effect. Moreover, local extrema are observed in the mobility profile as the double layer thickness varies, which is absent in previous theoretical study which neglected the polarization effect. An interesting phenomenon is observed: a less charged particle can even move faster than a highly charged one at some situation, which is also attributed to the polarization effect. The poorer the permeability of the polyelectrolyte or the polymer gel, the slower the particle motion in general, due to the increase of the hydraulic drag force. On the other hand, we found that the charge-regualtion phenomena has dramatic impact on the elctric condition of the particle. The higher the number of functional groups and the dissociation constant of the functional groups, the greater the charge of the particle; yet the higher the pH of the solution, the lower the charge of the particle.
Subjects
Electrophoresis
Diffusiohproresis
Charge-Regulation Phenomena
Gel-Electrophoresis
Soft Matter
Double Layer Polarization Effect
Type
thesis
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