Enhanced Adsorption of Epoxy‐Functional Nanoparticles onto Stainless Steel Significantly Reduces Friction in Tribological Studies

György, Csilla; Kirkman, Paul M.; Neal, Thomas J.; Chan, Derek H. H.; Williams, Megan; Smith, Thomas Aneurin; Growney, David J.; Armes, Steven P.

doi:10.1002/ange.202218397

Cited by 3 publications

(3 citation statements)

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“…88 Similarly, a significantly lower friction coefficient was observed within the boundary lubrication regime when conducting tribology experiments on epoxy-functionalized diblock copolymer nanoparticles covalently attached onto a planar stainlesssteel substrate relative to comparable measurements performed using similar nanoparticles bearing no epoxy groups. 67 Nevertheless, we posit that friction force studies via AFM are ideally suited for probing subtle differences in surface roughness for the nanoparticle-decorated brush surfaces reported herein. In this context, an interesting finding was reported by Penã-Paraś et al, who used wear measurements to assess friction for a series of particle lubricants.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…This approach led to measurement of mean surface coverages of 31–38% (Figure S16). Such data are comparable to that reported in the literature for nanoparticle adsorption onto other polymer brushes − or bare substrates ,, via electrostatic interactions or covalent bond formation. Curiously, visual analysis of the AFM images acquired for the dried nanoparticle-coated surfaces indicated a notably higher degree of coverage.…”

Section: Resultsmentioning

confidence: 99%

“…For example, vulcanized rubber coated with poly(methyl methacrylate) particles (at similar surface coverages to those presented herein) exhibited a monotonic reduction in friction with increasing particle size . Similarly, a significantly lower friction coefficient was observed within the boundary lubrication regime when conducting tribology experiments on epoxy-functionalized diblock copolymer nanoparticles covalently attached onto a planar stainless-steel substrate relative to comparable measurements performed using similar nanoparticles bearing no epoxy groups . Nevertheless, we posit that friction force studies via AFM are ideally suited for probing subtle differences in surface roughness for the nanoparticle-decorated brush surfaces reported herein.…”

Section: Resultsmentioning

confidence: 99%

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Adsorption of Aldehyde-Functional Diblock Copolymer Spheres onto Surface-Grafted Polymer Brushes via Dynamic Covalent Chemistry Enables Friction Modification

et al. 2023

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Dynamic covalent chemistry has been exploited to prepare numerous examples of adaptable polymeric materials that exhibit unique properties. Herein, the chemical adsorption of aldehyde-functional diblock copolymer spherical nanoparticles onto amine-functionalized surface-grafted polymer brushes via dynamic Schiff base chemistry is demonstrated. Initially, a series of cis-diol-functional sterically-stabilized spheres of 30–250 nm diameter were prepared via reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization. The pendent cis-diol groups within the steric stabilizer chains of these precursor nanoparticles were then oxidized using sodium periodate to produce the corresponding aldehyde-functional spheres. Similarly, hydrophilic cis-diol-functionalized methacrylic brushes grafted from a planar silicon surface using activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) were selectively oxidized to generate the corresponding aldehyde-functional brushes. Ellipsometry and X-ray photoelectron spectroscopy were used to confirm brush oxidation, while scanning electron microscopy studies demonstrated that the nanoparticles did not adsorb onto a cis-diol-functional precursor brush. Subsequently, the aldehyde-functional brushes were treated with excess small-molecule diamine, and the resulting imine linkages were converted into secondary amine bonds via reductive amination. The resulting primary amine-functionalized brushes formed multiple dynamic imine bonds with the aldehyde-functional diblock copolymer spheres, leading to a mean surface coverage of approximately 0.33 on the upper brush layer surface, regardless of the nanoparticle size. Friction force microscopy studies of the resulting nanoparticle-decorated brushes enabled calculation of friction coefficients, which were compared to that measured for the bare aldehyde-functional brush. Friction coefficients were reasonably consistent across all surfaces except when particle size was comparable to the size of the probe tip. In this case, differences were ascribed to an increase in contact area between the tip and the brush-nanoparticle layer. This new model system enhances our understanding of nanoparticle adsorption onto hydrophilic brush layers.

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Section: ■ Results and Discussionmentioning

confidence: 99%