Finally, the formation of a load-bearing tribofilm at the rubbing interface was confirmed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. High-contact-stress ball-on-flat reciprocating sliding tribological tests at 100 ☌ showed significant reductions in both the coefficient of friction (up to 38%) and wear volume (up to 90% for iron flat) for transparent, homogeneous dispersions of hairy NPs in PAO at a concentration of 1.0 wt % compared with neat PAO. Whereas poly(n-hexyl methacrylate) hairy NPs cannot be dispersed in PAO under ambient conditions or at 80 ☌, interestingly, poly(2-ethylhexyl methacrylate) hairy NPs can be dispersed in PAO at 80 ☌ but not at room temperature, with a reversible clear-to-cloudy transition observed upon cooling. We found that hairy NPs with sufficiently long alkyl pendant groups (containing >8 carbon atoms, such as 12, 13, 16, and 18 in this study) could be readily dispersed in poly(alphaolefin) (PAO), more » forming clear, homogeneous dispersions, and exhibited excellent stability at low and high temperatures as revealed by visual inspection and dynamic light scattering studies. The hairy NPs were prepared by surface-initiated reversible addition–fragmentation chain transfer polymerization from trithiocarbonate chain transfer agent (CTA)-functionalized silica NPs in the presence of a free CTA. This paper reports on the synthesis of a series of poly(alkyl methacrylate) brush-grafted, 23 nm silica nanoparticles (hairy NPs) and the study of the effect of alkyl pendant length on their use as oil lubricant additives for friction and wear reduction. Notably, wear volume reduction of up to 80% compared to the oil-soluble control poly(dodecyl methacrylate) is observed. Depending on the IL structure, VIIs containing up to 20 % mole IL are soluble in PAO (grade 4), and demonstrate friction-and-wear reduction, compared to a conventional oil-soluble PAMA. The structure of the IL, including more » the cation, the anion, and the spacer’s length separating the IL from the methacrylate group, plays an important role in the resulting polymer solubility in PAO (poly-alpha olefin), solution rheology, and friction-and-wear behavior. In this work, methacrylate type ionic liquid (IL) monomers containing ammonium or imidazolium cations and two different counter-anions were synthesized and used as co-monomers to obtain functional poly(alkyl methacrylates) (PAMAs) as viscosity index improvers (VII) additives for lubricants. Oil-miscible single molecule ionic liquids (ILs) are reported to perform well as neat lubricants and as additives in lubricating base oils. (ANL), Argonne, IL (United States) Sponsoring Org.: USDOE Office of Energy Efficiency and Renewable Energy (EERE) USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V) OSTI Identifier: 1247941 Alternate Identifier(s): OSTI ID: 1332611 OSTI ID: 1391919 Report Number(s): PNNL-SA-113593 Journal ID: ISSN 0021-8995 VT0604000 CEVT240 Grant/Contract Number: AC05-00OR22725 AC05-76RL01830 AC02-06CH11357 Resource Type: Journal Article: Accepted Manuscript Journal Name: Journal of Applied Polymer Science Additional Journal Information: Journal Volume: 133 Journal Issue: 26 Journal ID: ISSN 0021-8995 Publisher: Wiley Country of Publication: United States Language: English Subject: 36 MATERIALS = ,ĭespite the growing research field of polymeric ionic liquids used as materials for applications such as electrolytes and energy materials, catalysts, separation aides, and carbon materials, reports of lipophilic polymeric ionic liquids are essentially nonexistent. (PNNL), Richland, WA (United States) Argonne National Lab. (ORNL), Oak Ridge, TN (United States) Pacific Northwest National Lab. Publication Date: Research Org.: Oak Ridge National Lab. Unfortunately, increased wear rates were observed for these star-shape PAMAs in the boundary lubrication regime suggesting pressure sensitive conformations may exist. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Star-shape PAMAs, as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regimes. Observations of the polymer-oil blends suggest that stars with less than four arms are favorable as a viscosity index improver (VII), though molecular weight dominates viscosity related effects. Well-defined star-shape PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core-first strategy from multi-functional head-groups. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Star-shape poly(alkyl methacrylate)s (PAMAs) were prepared and blended into an additive free engine oil to assess the structure-property relationship between macromolecular structure and lubricant performance.
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