End-grafted sugar chains as aqueous lubricant additives
Synthesis and macrotribological tests of poly(l-lysine)-graft-dextran (PLL-g-dex) copolymers
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Date
2009
Publication Type
Journal Article
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yes
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Abstract
Comb-like graft copolymers with carbohydrate side chains have been developed as aqueous lubricant additives for oxide-based tribosystems, in an attempt to mimic biological lubrication systems, whose surfaces are known to be covered with sugar-rich layers. As adopted in the previous studies of the graft copolymer poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), which showed both excellent lubricating and antifouling properties, a similar approach was chosen to graft dextran chains onto the same backbone, thus generating PLL-g-dex. PLL-g-dex copolymers readily adsorb from aqueous solution onto negatively charged oxide surfaces. Tribological characterization at the macroscopic scale, either under pure sliding conditions or a mixed sliding/rolling contact regime, shows that PLL-g-dex is very effective for the lubrication of oxide-based tribosystems. The relative lubricating capabilities of PLL-g-dex copolymers compared with PLL-g-PEG copolymers were observed to be highly dependent on the molecular structure of the copolymers (in particular, side-chain density along the backbone) and the measurement conditions (in particular, time between tribocontacts); the PLL-g-dex copolymers with a low degree of grafted side chains (≤20% grafting of available protonated primary amine groups along the backbone) showed better lubricating performance than their PLL-g-PEG counterparts at high tribocontact frequency (≥ca. 0.32 Hz). © 2008 Springer Science+Business Media, LLC.
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published
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Journal / series
Volume
33 (2)
Pages / Article No.
83 - 96
Publisher
Springer
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Subject
Aqueous lubrication; Boundary lubrication; Biomimetic lubricant additives; Poly(L-lysine)-g-dextran
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03389 - Spencer, Nicholas (emeritus) / Spencer, Nicholas (emeritus)
Notes
Received 19 September 2008, Accepted 8 December 2008, Published online 30 December 2008. It was possible to publish this article open access thanks to a Swiss National Licence with the publisher