Interpolyelectrolyte Complex Dissociation vs Polyelectrolyte Desorption from Oppositely Charged Surface upon Salt Addition

The Journal of Physical Chemistry B, vol. 124, pp. 914–920

Abstract

The structure of complexes formed by oppositely charged polyelectrolytes and adsorbed layers on charged surfaces is sensitive to low-molecular-weight salt. Furthermore, if the concentration exceeds some threshold value, the complexes and adsorbed chains can be “dissolved”. This is due to the screening of the electrostatic interactions between charged units. In the current paper, we perform a comparative analysis of “dissolution” (dissociation) of complexes and layers upon addition of salt. For this, the conventional Brownian dynamics of computer simulations is used. We demonstrate that the complex based on linear chains dissociates at lower salt concentration than that required for desorption of equivalent chains from an oppositely charged surface. The physical reason is the difference in the symmetry of the electric field, which binds the chains into the complex (layer). In the salt-free regime, the intensity of the electric field (and attractive force) between two linear chains decays with the distance R between them, like for two spherical objects, ∼ R –2, if R is bigger than the characteristic size of the chain. On the contrary, the attractive force of the chain to the infinite surface does not depend on the distance to the surface (the electric field is constant). Therefore, if attractive forces in the condensed states of the two systems are equal, one needs to add more salt to screen the constant force than the decaying one. The computer simulation results on the adsorption of the chains were compared with the experimental data obtained for adsorption of cationic poly(4-vinylpyridine) on the surface of anionic liposomes. Good quantitative agreement was achieved.

Authors 2

1. Ivan V. Portnov Aachen DWI - Leibniz Institute for Interactive Materials

   DWI – Leibniz Institute for Interactive Materials · Russian Academy of Sciences · Lomonosov Moscow State University · A. N. Nesmeyanov Institute of Organoelement Compounds

   Affiliation as printed

   A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991, Russian Federation

   DWI—Leibniz Institute for Interactive Materials, Aachen 52056, Germany

   Physics Department, Lomonosov Moscow State University, Moscow 119991, Russian Federation

2. Igor I. Potemkin corresponding Aachen DWI - Leibniz Institute for Interactive Materials

   DWI – Leibniz Institute for Interactive Materials · Lomonosov Moscow State University · South Ural State University

   Affiliation as printed

   DWI—Leibniz Institute for Interactive Materials, Aachen 52056, Germany

   National Research South Ural State University, Chelyabinsk 454080, Russian Federation

   Physics Department, Lomonosov Moscow State University, Moscow 119991, Russian Federation