Electrophoresis of a soft particle with a hydrophobic rigid core decorated with a soft-step and partially ion-penetrable polymer layer

Abstract

On the basis of flat-plate formalism, we present an analytical theory for the electrophoresis of soft particles consisting of a hydrophobic inner core decorated with a layer of inhomogeneously distributed polymer segments. Biocolloids or bio-compatible drug delivery vehicles often carry the non-wettable or hydrophobic inner core. In addition, due to electrostatic swelling/shrinking processes, a spatially varying heterogeneity can be seen in the monomer distribution as well as charge properties of the peripheral polyelectrolyte layer (PEL). We adopt the soft-step function to model the chemical and structural anisotropy of the peripheral PEL. In addition, the PEL for the aforementioned bio-systems immersed in aquatic microenvironment often induces dielectric gradient-mediated ion partitioning effect, which in turn leads to the PEL to be partially ion penetrable. Within the Debye–Hückel electrostatic framework, we derive a general expression for electrophoretic mobility of a soft particle considering the combined impacts of hydrophobicity of the inner core, inhomogeneously distributed segment distribution accompanied by chemical heterogeneity and ion partitioning effect. We further derived asymptotic limits of the more generic results detailed here under several electrostatic and hydrodynamic conditions.