Electrokinetic fingerprinting of grafted polyelectrolyte layers—a theoretical approach

• Published in: Advances in colloid and interface science Vol. 122; no. 1; pp. 93 - 105
• Main Authors: Dukhin, Stanislav S., Zimmermann, Ralf, Werner, Carsten
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 25.09.2006; Elsevier
• Subjects: Applied sciences; Donnan potential; Electric Conductivity; Electrochemistry - methods; Electrokinetic fingerprinting; Electrokinetics; Electrolytes - chemistry; Electrophoresis - methods; Electrophoresis, Capillary; Exact sciences and technology; Grafted polyelectrolyte layers; Hydrogen-Ion Concentration; Kinetics; Micelles; Models, Chemical; Models, Statistical; Models, Theoretical; Organic polymers; Osmosis; Physicochemistry of polymers; Properties and characterization; Research Design; Soft surfaces; Surface conductivity; Surface potential; Surface Properties; Surface-Active Agents; Zeta potential; Soft surfaces; Zeta potential; Surface conductivity; Electrokinetics; Donnan potential; Electrokinetic fingerprinting; Grafted polyelectrolyte layers; Surface potential; Transport properties; Electrical properties; Theoretical study; Modeling; Surface electrical conductivity; Polyelectrolyte; Ionic strength; Electrophoresis; Electrokinetic potential; Spherical particle; Graft polymers
• ISSN: 0001-8686; 1873-3727
• DOI: 10.1016/j.cis.2006.06.009

Electrokinetic fingerprinting (EF) was introduced by Marlow and Rowell [Marlow BJ, Rowel RL. Langmuir 1990;6:1088] for the comprehensive characterization of charged particle surfaces. Afterwards, EF was applied by many groups for the characterization of “hard” (i.e. non-swelling) surfaces. However, the advantages of EF could not yet utilized for the characterization of grafted polyelectrolyte layers (PL) since the theoretical background was not yet elaborated. A theory for the characterization of PL at complete dissociation of the functional groups was developed by Ohshima [Adv Colloid Interface Sci 1995;62:189] and later extended by Dukhin et al. [Dukhin S, Zimmermann R, Werner C. J Colloid Interface Sci 2005;286:761] for any degree of dissociation. Further progress in the characterization of soft surfaces may be achieved by combining EF and surface conductivity (SC) measurements. Both theory and experiment demonstrate that integrated measurements of SC and apparent zeta potential ζ a in broad ranges of pH and ionic strength provide information about Donnan potential Ψ D, surface charge, p K and surface potential Ψ 0, while the interpretation is more uncertain, when only ζ a is measured. This advanced method of PL characterization is established for PL grafted on flat surfaces. When PL are formed on spherical particles, the SC may be measured by means of conductometry and/or dielectric spectroscopy. However, the current theories can only be applied within a rather narrow range of the practically relevant conditions. To overcome this limitation, an unified approach to the theory of electrophoresis for spherical particles with grafted PL was elaborated taking into account the existence of two different electrokinetic models for soft surfaces. While one model is focused on hydrodynamic permeability of soft surface and disregards surface current, another model considers the surface current and disregards electrokinetic water transport within the soft surface layer. Unification became possible through generalization of the capillary osmosis theory over soft surfaces.