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Cited by 85Electrostatics and Colloid InteractionsPolymer Surface Interaction StudiesAdhesion, Friction, and Surface Interactions

Normal and Shear Forces between Adsorbed and Gelled Layers of Chitosan, a Naturally Occurring Cationic Polyelectrolyte

Kampf, Nir, Raviv, Uri, Klein, Jacob·2004·Macromolecules
DOI 10.1021/ma0303263
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Abstract

Using a mica surface force balance, we have measured the interactions between mica surfaces bearing chitosan (a common, naturally occurring, cationic polysaccharide; the average molecular weight of our sample was 6 × 10 5, degree of deacetylation 85%) adsorbed from acetic acid solution. We also introduced a polyionic cross-linking agent in order to cause gelation of the adsorbed layer. Both normal and shear interactions (the lateral forces acting between the surfaces as they slide past each other under compression) were measured in the two cases (freely adsorbed and cross-linked chitosan layers). Normal interactions between the adsorbed non-cross-linked chitosan layers were similar to previous reports of interactions between such layers; their shear interactions revealed a very low effective friction coefficient μ eff = ca. 0.003 at low compressions, increasing to ca. 0.07 at pressures of some atmospheres. We attribute the low friction to the weak interpenetration between the layers arising from steric effects and counterion osmotic pressures, together with the presence of hydration sheaths about the charged polyelectrolyte segments, which are known to provide efficient local lubrication. The higher friction on strong compressions is attributed to bridging effects. For the case of the cross-linked layer, normal interactions revealed longer ranged and more repulsive forces, due probably to the network formation resulting in a higher effective modulus of the layers. Frictional forces between the rubbing cross-linked layer were much higher than for the non-cross-linked chitosan, an effect we attribute to increased segmental friction arising from attractive interactions between the cross-linking points; this is also consistent with our observation that for the cross-linked layers significant hysteresis was observed when measuring normal interactions on approach and separation of the layers, an effect that was absent for the case of the non-cross-linked adsorbed layers. Refractive index measurements revealed an adsorbance of 1.2 ± 0.4 mg/m 2 of the polymer on each mica surface, consistent with expectations for cationic polymers adsorbed on solid surfaces.

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  • Bridging occurs when a chain from one adsorbed layer adsorbs to the opposing surface; sliding drags bridging chains, leading to energy dissipation and higher friction.

    “Such bridging occurs when a chain from one adsorbed layer adsorbs also to the opposing surface: When the surfaces slide past each other, the bridging chains are dragged past the surfaces onto which they are adsorbed, leading to energy dissipation and thus to higher friction [30, 77, 78].”

    From Hydration lubrication (2013) · cites this paper as [77]

  • Charged brushes provide considerably better lubrication up to higher compression than either neutral brushes (in organic or aqueous media) or adsorbed polyelectrolytes.

    “As indicated by the different data symbols and the cartoons in Fig. 9, the charged brushes provide considerably better lubrication up to higher compression than either neutral brushes -whether in organic or in aqueous media [75, 76] -or than adsorbed polyelectrolytes [77, 78].”

    From Hydration lubrication (2013) · cites this paper as [77]

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Authors
Kampf, N., Raviv, U., & Klein, J.
Affiliations
University of Oxford (GB)
ORCID
Venue
Macromolecules
Publisher
American Chemical Society (ACS)
Published
2004-01-20
Volume
37
Issue
3
Pages
1134-1142
ISSN
  • 0024-9297 (ISSN-L)
  • 1520-5835
DOI
10.1021/ma0303263
OpenAlex
W1988559668
Cited by
85
References
32
Citations by year
2025: 2 · 2023: 4 · 2022: 3 · 2021: 3 · 2020: 1 · 2019: 4 · 2018: 3 · 2017: 3 · 2016: 4 · 2015: 4 · 2014: 8 · 2013: 9 · 2012: 2
FWCI
3.56
Type
journal article
Language
en
Open access
closed
Locations
Macromolecules (publishedVersion)
Topics
  • Physical Sciences › Chemistry › Physical and Theoretical Chemistry › Electrostatics and Colloid Interactions
  • Physical Sciences › Materials Science › Surfaces, Coatings and Films › Polymer Surface Interaction Studies
  • Physical Sciences › Engineering › Mechanics of Materials › Adhesion, Friction, and Surface Interactions
Keywords
chitosan, interlayer friction, steric repulsion, bridging interactions, hysteresis, adsorption density, refractive index

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