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Single Molecule Experiments Visualizing Adsorbed Polyelectrolyte Molecules in the Full Range of Mono- and Divalent Counterion Concentrations

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journal contribution
posted on 06.10.2010, 00:00 by Yuri Roiter, Oleksandr Trotsenko, Viktor Tokarev, Sergiy Minko
This work provides direct experimental verification (on the level of single molecules) for the behavior of hydrophobic polyelectrolyte chains adsorbed at a solid−liquid interface in the full range of possible salt concentrations: (a) in a dilute salt solution, PE chains possess an extended coil conformation visualized as adsorbed 2D-equilibrated coils; (b) in a moderate salt concentration range, the polymer coil shrinks and approaches the dimensions of a polymer coil under θ-conditions and the chains are visualized as adsorbed 3D-projected coils; (c) at high salt concentrations, the polymer coils reexpand and the molecules are visualized as 2D-equilibrated extended coils; however, (d) reexpansion is limited in the presence of multivalent counterions, presumably due to the bridging of the polymer coils by the counterions.