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Salt Dependence of the Tribological Properties of a Surface-Grafted Weak Polycation in Aqueous Solution

Lookup NU author(s): Professor Mark GeogheganORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


© 2017, The Author(s).The nanoscopic adhesive and frictional behaviour of end-grafted poly[2-(dimethyl amino)ethyl methacrylate] (PDMAEMA) films (brushes) in contact with gold- or PDMAEMA-coated atomic force microscope tips in potassium halide solutions with different concentrations up to 300 mM is a strong function of salt concentration. The conformation of the polymers in the brush layer is sensitive to salt concentration, which leads to large changes in adhesive forces and the contact mechanics at the tip–sample contact, with swollen brushes (which occur at low salt concentrations) yielding large areas of contact and friction–load plots that fit JKR behaviour, while collapsed brushes (which occur at high salt concentrations) yield sliding dominated by ploughing, with conformations in between fitting DMT mechanics. The relative effect of the different anions follows the Hofmeister series, with I− collapsing the brushes more than Br− and Cl− for the same salt concentration.

Publication metadata

Author(s): Raftari M, Zhang ZJ, Carter SR, Leggett GJ, Geoghegan M

Publication type: Article

Publication status: Published

Journal: Tribology Letters

Year: 2017

Volume: 66

Issue: 1

Online publication date: 05/12/2017

Acceptance date: 23/11/2017

Date deposited: 19/12/2019

ISSN (print): 1023-8883

ISSN (electronic): 1573-2711

Publisher: Springer New York LLC


DOI: 10.1007/s11249-017-0963-0


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