Load Induced Microstructure Evolution and Friction in an Organic Monolayer Self-assembled on a Silicon Substrate

Khatri, Om P.; Biswas, Sushanta

doi:10.1007/s11249-008-9378-2

Cited by 3 publications

(3 citation statements)

References 53 publications

(79 reference statements)

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“…erties which play a fundamental role in a wide range of technological applications. [18][19][20][21][22] Various experimental methods have been used to study the friction of the SAMs at molecular level. These include AFM/friction force microscopy (FFM), 20 chemical force microscopy, SFG spectroscopy, 21 surface force apparatus, and IFM.…”

Section: Introductionmentioning

confidence: 99%

Frictional properties of two alkanethiol self assembled monolayers in sliding contact: Odd-even effects

Ramin

Jabbarzadeh

2012

The Journal of Chemical Physics

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Using molecular dynamics simulation, we have investigated the structural effects on the frictional properties of self assembled monolayers (SAM) of n-alkanethiols [CH(3)(CH(2))(n-1)SH, n = 12-15] in SAM-SAM contacts attached on Au (111) substrates. We have observed an odd-even effect where friction coefficient for SAM-SAM contacts with n = odd showed consistently higher values than those with n = even. This odd-even effect is independent of the sliding velocity and the relative tilt directions of the SAMs, and persists over a much higher pressure range than that reported before for SAM-Au contacts [L. Ramin and A. Jabbarzadeh, Langmuir 28, 4102-4112 (2012)]. For odd systems higher gauche defects were shown to be the possible source of high friction coefficient. Under the same load and shear rates (comparable sliding velocities), SAM-SAM contacts show mostly higher friction compared to SAM-Au contacts. For SAM-SAM contacts, a more significant increase of friction occurs at higher shear rates due to a shift in the tilt orientation angle. We show SAM-SAM contacts with misaligned relative tilt orientation angle (∼45°-90°) have considerably lower friction compared with those whose tilt orientation angles are almost aligned in the opposite directions and parallel to the shear.

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Section: Introductionmentioning

confidence: 99%

Frictional properties of two alkanethiol self assembled monolayers in sliding contact: Odd-even effects

Ramin

Jabbarzadeh

2012

The Journal of Chemical Physics

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“…Khatri and Biswas studied the load-induced microstructure evolution and friction in an organic monolayer self-assembled on a silicon substrate. 8 observed that the area averaged friction force was dominated by the low-friction crystalline tiles at low loads, while high friction was dominated by amorphous tiles at high loads.…”

Section: Introductionmentioning

confidence: 93%

“…While the state of the surfactant coating (crystalline vs amorphous) affects the tribological behavior, shear forces can, at the same time, affect the structure of the surfactant and particularly induce its crystallization. Khatri and Biswas studied the load-induced microstructure evolution and friction in an organic monolayer self-assembled on a silicon substrate . They observed that the area averaged friction force was dominated by the low-friction crystalline tiles at low loads, while high friction was dominated by amorphous tiles at high loads.…”

Section: Introductionmentioning

confidence: 99%

Electric Response of CuS Nanoparticle Lubricant Additives: The Effect of Crystalline and Amorphous Octadecylamine Surfactant Capping Layers

Liu

Friedman

et al. 2019

Langmuir

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Octadecylamine-coated CuS nanoparticles were designed and confirmed to play an important role in their electric response and boundary lubrication in the ester lubricant. For the case of CuS nanoparticles coated with crystalline surfactant, the surface potential is 18.47 ± 0.99 mV higher than with amorphous surfactant, owing to the random chain conformations of the octadecylamine molecules. When used as a lubricant additive, CuS nanoparticles (in the form of nanoplates or nanoarrays) with a crystalline surfactant were positively charged due to the presence of the amino headgroup in octadecylamine. The observed friction coefficient decreased from 0.18 to 0.09 and 0.05, respectively, when negative potential (for the copper lower pair) was applied across untreated CuS nanoparticles. However, thermally treated CuS nanoparticles showed good lubricating effect, but almost no effect of potential control since the amino groups were obscured by the disordered carbon chains, hindering electron transfer and weakening the response to externally applied electric field.

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Molecular friction dissipation and mode coupling in organic monolayers and polymer films

Knorr

Widjaja

Acton

et al. 2011

The Journal of Chemical Physics

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The impact of thermally active molecular rotational and translational relaxation modes on the friction dissipation process involving smooth nano-asperity contacts has been studied by atomic force microscopy, using the widely known Eyring analysis and a recently introduced method, dubbed intrinsic friction analysis. Two distinctly different model systems, i.e., monolayers of octadecyl-phosphonic acid (ODPA) and thin films of poly(tert-butyl acrylate) (PtBA) were investigated regarding shear-rate critical dissipation phenomena originating from diverging mode coupling behaviors between the external shear perturbation and the internal molecular modes of relaxation. Rapidly (ODPA) versus slowly (PtBA) relaxing systems, in comparison to the sliding rate, revealed monotonous logarithmic and nonmonotonous spectral shear rate dependences, respectively. Shear coupled, enthalpic activation energies of 46 kJ∕mol for ODPA and of 35 and ∼65 kJ∕mol for PtBA (below and above the glass transition) were found that could be attributed to intrinsic modes of relaxations. Also, entropic energies involved in the cooperative backbone mobility of PtBA could be quantified, dwarfing the activation energy by more than a factor of five. This study provides (i) a material specific understanding of the molecular scale dissipation process in shear compliant substances, (ii) analyses of material intrinsic shear-rate mode coupling, shear coordination and energetics, (iii) a verification of Eyring's model applied to tribological systems toward material intrinsic specificity, and (iv) a valuable extension of the Eyring analysis for complex macromolecular systems that are slowly relaxing, and thus, exhibit shear-rate mode coupling.

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Load Induced Microstructure Evolution and Friction in an Organic Monolayer Self-assembled on a Silicon Substrate

Cited by 3 publications

References 53 publications

Frictional properties of two alkanethiol self assembled monolayers in sliding contact: Odd-even effects

Frictional properties of two alkanethiol self assembled monolayers in sliding contact: Odd-even effects

Electric Response of CuS Nanoparticle Lubricant Additives: The Effect of Crystalline and Amorphous Octadecylamine Surfactant Capping Layers

Molecular friction dissipation and mode coupling in organic monolayers and polymer films

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