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Influence of salt on the solution dynamics of a phosphorylcholine-based polyzwitterion

Lookup NU author(s): Professor Mark GeogheganORCiD



This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).


© 2016 The diffusion of a polyzwitterion, poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), in aqueous solution containing different alkali halides was studied by fluorescence correlation spectroscopy at single molecule level. It was found that the halide anion has a greater effect on the radius of zwitterionic PMPC molecules than alkali cations, which is due to the mechanism by which PMPC molecules interact with the surrounding hydrogen bond network of water molecules and adsorbed ions. With the addition of salt, the size of PMPC remains constant while its diffusion coefficient is reduced slightly, although larger cations (e.g. K+) result in slightly increased diffusion coefficient for 1 M potassium chloride-based solutions. This enhanced diffusion coefficient is attributed to the decrease in the viscosity of the aqueous solution on the addition of salt. When the counter-ion was varied in potassium-based salts, different effects were observed for different anions, resulting a reduction in the diffusion coefficient as a function of salt concentration. This reduction was modest for KBr, but significant for KI. Overall, no discernible changes were observed as the size of the PMPC coil was varied, except in case of KI for which a significant increase was observed at higher ionic strength. Divalent cations (Ca2+ and Mg2+), produced similar effects to those found for monovalent cations. These effects are explained by the interaction of PMPC with the hydrogen bond network of water molecules and with the adsorbed ions.

Publication metadata

Author(s): Zhang ZJ, Madsen J, Warren NJ, Mears M, Leggett GJ, Lewis AL, Geoghegan M

Publication type: Article

Publication status: Published

Journal: European Polymer Journal

Year: 2017

Volume: 87

Pages: 449-457

Print publication date: 01/02/2017

Online publication date: 21/12/2016

Acceptance date: 02/12/2016

Date deposited: 05/08/2021

ISSN (print): 0014-3057

ISSN (electronic): 1873-1945

Publisher: Elsevier Ltd


DOI: 10.1016/j.eurpolymj.2016.12.001


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