Shielding behavior of electrokinetic properties of polystyrene latex particle by the adsorption of neutral poly(ethylene oxide)

To understand the shielding of electrokinetics of colloidal particles by polymer coating, we measured the electrophoretic mobility of negatively charged polystyrene sulfate latex (PSL) adsorbed with electrostat-ically neutral polyethylene oxide (PEO) chains with various molecular weights under different ionic strengths. We confirmed that substantial adsorbed neutral polymer on the particle surface would decrease the absolute value of electrophoretic mobility. Even though the polymer layer is sufficiently thicker compared to the thickness of electric double layer (EDL), the electrophoretic mobility (EPM) never vanishes, which indicates the incompleteness of electrokinetic shielding by an adsorbed neutral polymer. To relate such interesting phenomena, a simple mathematical model has been proposed to evaluate the electrophoretic mobility, assuming the presence of a scaling structure of adsorbed permeable polymer layer does not influence the Poisson-Boltzmann distribution of ions in the electric double layer (EDL). An analytical expression of electrophoretic mobility under Debye-Huckel approximation has been derived using the method of Ohshima-Kondo theory, which successfully justifies the experimentally obtained data. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

In this study, the effect of polymer coating on the electrokinetic shielding of colloidal particles was investigated by measuring the electrophoretic mobility of negatively charged polystyrene sulfate latex (PSL) particles adsorbed with electrostatically neutral polyethylene oxide (PEO) chains of various molecular weights under different ionic strengths. The results showed that the presence of substantial adsorbed neutral polymer on the particle surface reduced the absolute value of electrophoretic mobility. However, even with a sufficiently thick polymer layer compared to the electric double layer (EDL), the electrophoretic mobility never vanished, indicating the incomplete electrokinetic shielding by the adsorbed neutral polymer. A mathematical model was proposed to explain this phenomenon, and the experimentally obtained data were successfully justified using an analytical expression derived from the Ohshima-Kondo theory under the Debye-Huckel approximation.