An analysis on electrophoretic mobility of hydrophobic polystyrene particles with low surface charge density: effect of
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An analysis on electrophoretic mobility of hydrophobic polystyrene particles with low surface charge density: effect of hydrodynamic slip Motoyoshi Kobayashi 1 Received: 30 June 2020 / Accepted: 2 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The electrophoretic mobility of hydrophobic polystyrene particles in aqueous monovalent electrolyte solutions is analyzed using standard electrokinetic equations with a hydrodynamic boundary condition called the Navier slip condition, in which a fictitious slip length is a parameter for a slip velocity, at the particle surface. The standard electrokinetic equations underestimate the mobility of polystyrene particles bearing lower surface charge density when using the values of surface charge density from titration and a no-slip boundary condition. The introduction of the slip length of a few nanometer increases the magnitude of electrophoretic mobility and leads to the agreement between experimental mobility and theoretical mobility. The slip length increases with increasing the distance between chargeable groups on the particle surface. This result indicates the increase in hydrophobicity for the surface of polystyrene particle with the lower number of chargeable sites. Keywords Electrokinetics . Distancebetween surface neighboringcharges . Hydrodynamicslipboundarycondition . Doublelayer polarization
Introduction Since the finding of electrophoresis of colloidal particles, theoretical works have been developed to describe the relationship between electrophoretic mobility and surface/zeta potential [1–5]. The analytical and numerical solutions of a set of standard equations for electrokinetics including hydrodynamics, ion transport, and electrostatics are now available [6–8]. The validity of such solutions has been examined for monodispersed sphere with known surface charge density and diameter in well-defined aqueous solutions [9–12]. Nowadays, solutions of the standard equations have been extended and successfully applied to the electrophoretic mobility of rod-like particles, nanofiber, and proteins [13–16]. The evaluated charging behaviors from electrophoretic mobility are crucial for the discussion of aggregation and deposition Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00396-020-04716-2) contains supplementary material, which is available to authorized users. * Motoyoshi Kobayashi [email protected] 1
Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
of various colloidal particles with/without absorbable ionic matters on the basis of the Derjaguin-Landau-VerweyOverbeek theory [17–25]. Therefore, it has been important to add better insight into electrophoresis in colloid and polymer science and related fields. Polystyrene (PS) latex spheres with sulfate/sulfonate groups are used as standard colloidal particles, because they are monodispersed in size, their surface charge is consta
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