Mediation of the Nanotribological Properties of Cellulose by Chitosan Adsorption
2009 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 3, 645-650 p.Article in journal (Refereed) Published
Cellulosic model surfaces functionalized with chitosan, a naturally occurring cationic biomacromolecule, by in-situ adsorption have been studied with an atomic force microscope (AFM) in colloidal probe configuration. The interaction forces on approach and separation, as well as the nanotribological properties, were shown to be highly pH-dependent and a significant difference in the behaviour was seen before and after chitosan adsorption. In general, all forces on approach showed a highly repulsive interaction at shorter distances due to deformation of the probe. At high pH, before chitosan adsorption, a long-range electrostatic repulsion was observed, consistent with DLVO theory. However at low pH no electrostatic contribution was found before adsorption probably due to charge neutralization of carboxyl groups. After chitosan adsorption, repulsive forces acting over a much longer distance than predicted by DLVO theory were present at low pH. This effect was ascribed to chain extension of the chitosan species of which the magnitude and the range of the force increased dramatically with higher charge at low pH. In all cases, a typical saw-tooth patterned adhesion was present with pull-off events occurring at different separations. The frequency of these events after chitosan adsorption was greatly increased at longer distances. Additionally, the adsorbed chitosan markedly reduced the friction where the largest effect was a 7-fold decrease of the friction coefficient observed at low pH.
Place, publisher, year, edition, pages
USA: American Chemical Society , 2009. Vol. 10, no 3, 645-650 p.
AFM, QCM-D, cellulose, chitosan, nanotribology, surface forces, friction, adhesion, colloidal probe, polysaccharide interactions
IdentifiersURN: urn:nbn:se:kth:diva-10998DOI: 10.1021/bm801467wISI: 000264059400024ScopusID: 2-s2.0-65249099501OAI: oai:DiVA.org:kth-10998DiVA: diva2:233863
QC 201008042009-09-022009-09-022010-12-06Bibliographically approved