Charge regulation and energy dissipation while compressing and sliding a cross-linked chitosan hydrogel layer
2015 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 443, 162-169 p.Article in journal (Refereed) Published
Interactions between a silica surface and a surface coated with a grafted cross-united hydrogel made from chitosan/PAA multilayers are investigated, utilizing colloidal probe atomic force microscopy. Attractive double-layer forces are found to dominate the long-range interaction over a broad range of pH and ionic strength conditions. The deduced potential at the hydrogel/aqueous interface is found to be very low. This situation is maintained in the whole pH-range investigated, even though the degree of protonation of chitosan changes significantly. This demonstrates that pH-variations change the concentration of counterions within the hydrogel to keep the interior close to uncharged, which is similar to what has been observed for polyelectrolyte brushes. Changes in pH and ionic strength affect the adhesion force and the friction force between the silica surface and the hydrogel layer, but not the friction coefficient. This suggests that the main energy dissipation mechanism arises from processes occurring within the hydrogel layer, rather than at the silica/hydrogel interface, and we suggest that it is related to stretching of polymer chains between the cross-linking points. We also find that an increased cross-linking density, from 40% to 100%, in the hydrogel reduces the friction coefficient. (C) 2014 Elsevier Inc. All rights reserved.
Place, publisher, year, edition, pages
2015. Vol. 443, 162-169 p.
Chitosan, Hydrogel, Surface force, Friction, pH, Ionic strength
IdentifiersURN: urn:nbn:se:kth:diva-161087DOI: 10.1016/j.jcis.2014.12.003ISI: 000348696700021PubMedID: 25553574ScopusID: 2-s2.0-84920884287OAI: oai:DiVA.org:kth-161087DiVA: diva2:797968
FunderSwedish Research CouncilSwedish Foundation for Strategic Research
QC 201503252015-03-252015-03-092015-03-25Bibliographically approved