Main Chain Effects in Tetraol-Functionalized Perfluoropolyethers

Waltman, R. J.; Wiita, Connie

doi:10.2474/trol.10.262

Cited by 7 publications

(3 citation statements)

References 19 publications

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“…This characteristic difference between D-4OH and Z-tetraol was observed previously [14] and is verified in the current study. Waltman reported that the flexibility of the lubricant molecules, Fomblin and Demnum, depends on their main chain structure [4]. Therefore, the difference in effective Young's modulus obtained in this study can be attributed to the flexibility of the two lubricant molecules.…”

Section: Young's Modulus Of D-4oh Lubricant Filmsmentioning

confidence: 50%

“…To further increase the HDD capacity, it is necessary to decrease the PFPE lubricant film thickness to reduce the flying height of the magnetic head. Therefore, lubricants with various main-chain and end-group structures have been studied [1][2][3][4][5]. The properties of these lubricants are evaluated primarily on the basis of bonded ratio and surface energy, focusing on the adsorption conditions of the lubricant film; heat resistance, focusing on the evaporation property and decomposition at high temperature; molecular mobility, focusing on the replenishment property of the lubricant film; monolayer thickness, focusing on the physical thickness on the disk; and the properties that are evaluated in actual hard disk drives, such as lubricant pickup by the head slider.…”

Section: Introductionmentioning

confidence: 99%

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Effective Elastic Moduli of Magnetic Disks with Molecularly Thin Liquid Lubricant Films Determined Using Ar-Gas Cluster Ion Beam

et al. 2022

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To improve the reliability of the design of hard disk drives, this study aims to determine the effective elastic properties of disks with perfluoropolyether lubricant films on the diamond-like carbon overcoats of magnetic disks. However, the determination of the effective elastic modulus of multi-layered film from molecularly thin lubricant films (1.0 nm) and diamond-like carbon overcoats is extremely difficult because these layers are ultra-thin. Therefore, the method of etching in the depth direction with an Ar-gas cluster ion beam is proposed in this study. The lubricants D-4OH and Z-tetraol, comprising different main chains, are applied to the samples at varying thicknesses. Additionally, the D-4OH is UV-treated to vary the bonded film thickness. The effective Young's modulus of disk with D-4OH is approximately 60 and 20 GPa at 1.2 and 2.9 nm film thicknesses, respectively, whereas that of Z-tetraol is approximately 16 GPa at 1.2 nm film thickness, and exhibits less dependence on the film thickness than that of D-4OH. The effective Young's modulus of D-4OH increases with increasing bonded thickness. These results suggest a significant variation in the effective Young's modulus of disks with the lubricant film based on the film thickness, molecular structure, and adsorption state.

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Section: Young's Modulus Of D-4oh Lubricant Filmsmentioning

confidence: 50%

Section: Introductionmentioning

confidence: 99%

Effective Elastic Moduli of Magnetic Disks with Molecularly Thin Liquid Lubricant Films Determined Using Ar-Gas Cluster Ion Beam

et al. 2022

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“…End-functionalized linear perfluoropolyethers (PFPEs) have long served rigid magnetic media as the boundary lubricant of choice for tribological robustness related to head wear and contamination in the hard disk drive (HDD) [1][2][3]. During the last decade, several significant changes to the HDD have imposed on the chemical design of future boundary lubricant films.…”

Section: Introductionmentioning

confidence: 99%

Perfluoropolyether Boundary Lubricants Based on the Star Architecture

2018

Self Cite

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Star PFPE (perfluoropolyether) polymers based on an aromatic benzene core and a non-aromatic cyclotriphosphazene (CTP) core are investigated as boundary lubricant films on rigid magnetic media. The effect of the benzene and CTP cores on head-disk spacing are measured by the changes in the acoustic emission signal as a function of head-disk spacing at similar lubricant film thicknesses. The earlier head-disk contact observed with the CTP core is attributed in part to its larger size perpendicular to the plane of the disk surface. The adhesion of the benzene and CTP cores to the underlying carbon film is investigated by ab initio quantum chemistry. The nonaromatic nature of the CTP ring and the lack of steric accessibility to the CTP core nitrogen atoms prevent good adhesive interactions with the underlying carbon film. Conversely, the π-electrons of aromatic benzene create a quadrupole moment in the direction perpendicular to the plane of the benzene that can interact with the underlying carbon surface and hence provide weak adhesion. Electron-withdrawing and-donating substituents on the benzene ring can be used to exert a "push-pull" effect on the π-electrons to alter the strength of the intermolecular interactions to specific functional groups of the underlying carbon surface. These effects are visualized by mapping the electrostatic potential of the benzene core as a function of electron-withdrawing and-donating substituents and computing model dimer optimized geometries and intermolecular interaction energies. Finally, the thermal stability of the star PFPE polymers are quantified by measuring the evaporation rate of thin films (11 Å) as a function of time at the HDD temperature (~ 60°C). Thermogravimetric analyses (TGA) of the neat polymers also provide direction for improvement of the synthetic lubricants.

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A Numerical Simulation of PFPE Lubricant Kinetics in HAMR Air Bearing

Tom,

Cheng,

Bogy

2024

Tribol Lett

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This report investigates the kinetics of lubricant molecules in the HAMR air bearing to understand the initiation and growth of PFPE contamination on the head surface. The collisions with the air bearing induce three forces—drag, thermophoresis, and lift. Of these, we find that lift forces are negligible. Then, a sensitivity analysis of the remaining two forces reveals the conditions where they dominate. Further, a hybrid simulation strategy is utilized to track their movements. The results show that the contaminations (smear) highly depend on the interplay between the thermophoresis and drag forces. We then explain the mechanism of the formation of the various observed patterns. Finally, we offer some recommendations to exploit the air bearing to contain smear on the head.

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Main Chain Effects in Tetraol-Functionalized Perfluoropolyethers

Cited by 7 publications

References 19 publications

Effective Elastic Moduli of Magnetic Disks with Molecularly Thin Liquid Lubricant Films Determined Using Ar-Gas Cluster Ion Beam

Effective Elastic Moduli of Magnetic Disks with Molecularly Thin Liquid Lubricant Films Determined Using Ar-Gas Cluster Ion Beam

Perfluoropolyether Boundary Lubricants Based on the Star Architecture

A Numerical Simulation of PFPE Lubricant Kinetics in HAMR Air Bearing

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