title: Interactions between charged surfaces mediated by stiff, multivalent zwitterionic polymers.
abstract: The interaction between like-charged objects in electrolyte solutions can be heavily altered by the presence of multivalent ions which possess a spatially distributed charge. In this work, we examine the influence of stiff, multivalent zwitterionic polymers on the interaction between charged surfaces using a splitting field theory previously shown to be accurate for the weak to the intermediate to the strong electrostatic coupling regimes. The theory is compared to Monte Carlo simulations and good agreement is found between both approaches. For surface separations shorter than the polymer length, the polymers are mainly oriented parallel to the surfaces, and the surface-surface interaction is repulsive. When the surface separation is comparable to the length of polymers, the polymers have two main orientations. The first corresponds to the polymers adsorbed onto the surface with their centers located near to or in contact with the surface; the second corresponds to polymers which are perpendicular to the charged surfaces, bridging both surfaces and leading to an attractive force between them. Increasing the surface charge density leads to more pronounced attraction via bridging. At surface separations greater than the polymer length, the polymers in the center of the system are still mainly perpendicular to the surfaces, due to "chaining" between zwitterions that enable them to bridge the surfaces at larger separations. This leads to an attractive interaction between the surfaces with a range significantly longer than the length of the polymers.
authors.affiliation: Faculty of Health Sciences, University of Ljubljana, SI-1000 Ljubljana, Slovenia. klemen.bohinc@zf.uni-lj.si.
authors.forename: Klemen
authors.initials: K
authors.lastname: Bohinc
authors.affiliation: Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia. jurij.rescic@fkkt.uni-lj.si.
authors.forename: Jurij
authors.initials: J
authors.lastname: Reščič
authors.affiliation: Department of Chemical and Process Engineering, University of Strathclyde, James Weir Building, 75 Montrose Street, Glasgow G1 1XJ, UK. leo.lue@strath.ac.uk.
authors.forename: Leo
authors.initials: L
authors.lastname: Lue