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Title: Effects of star-shape poly(alkyl methacrylate) arm uniformity on lubricant properties

Abstract

Star-shaped 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. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well-defined star-shaped PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core-first strategy from multi-functional headgroups. Observations of the polymer-oil blends suggest that stars with less than four arms are favorable as a viscosity index improver (VII), and molecular weight dominates viscosity-related effects over other structural features. Star-shaped PAMAs, as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regime. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Furthermore, increased wear rates were observed for these star-shaped PAMAs in the boundary lubrication regime suggesting pressure-sensitive conformations may exist.

Authors:
 [1];  [2];  [3];  [1];  [2]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
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 SCIENCE

Citation Formats

Robinson, Joshua W., Qu, Jun, Erck, Robert, Cosimbescu, Lelia, and Zhou, Yan. Effects of star-shape poly(alkyl methacrylate) arm uniformity on lubricant properties. United States: N. p., 2016. Web. doi:10.1002/app.43611.
Robinson, Joshua W., Qu, Jun, Erck, Robert, Cosimbescu, Lelia, & Zhou, Yan. Effects of star-shape poly(alkyl methacrylate) arm uniformity on lubricant properties. United States. doi:10.1002/app.43611.
Robinson, Joshua W., Qu, Jun, Erck, Robert, Cosimbescu, Lelia, and Zhou, Yan. Tue . "Effects of star-shape poly(alkyl methacrylate) arm uniformity on lubricant properties". United States. doi:10.1002/app.43611. https://www.osti.gov/servlets/purl/1247941.
@article{osti_1247941,
title = {Effects of star-shape poly(alkyl methacrylate) arm uniformity on lubricant properties},
author = {Robinson, Joshua W. and Qu, Jun and Erck, Robert and Cosimbescu, Lelia and Zhou, Yan},
abstractNote = {Star-shaped 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. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well-defined star-shaped PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core-first strategy from multi-functional headgroups. Observations of the polymer-oil blends suggest that stars with less than four arms are favorable as a viscosity index improver (VII), and molecular weight dominates viscosity-related effects over other structural features. Star-shaped PAMAs, as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regime. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Furthermore, increased wear rates were observed for these star-shaped PAMAs in the boundary lubrication regime suggesting pressure-sensitive conformations may exist.},
doi = {10.1002/app.43611},
journal = {Journal of Applied Polymer Science},
number = 26,
volume = 133,
place = {United States},
year = {Tue Mar 29 00:00:00 EDT 2016},
month = {Tue Mar 29 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
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Citation Metrics:
Cited by: 1work
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  • Here, 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. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well-defined star-shape PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core-first strategy from multi-functional head-groups. 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 over other structural features.more » Star-shape PAMAs, as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regimes. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Unfortunately, increased wear rates were observed for these star-shape PAMAs in the boundary lubrication regime suggesting pressure sensitive conformations may exist.« less
  • 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. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well-defined star-shape PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core-first strategy from multi-functional head-groups. 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. Star-shape PAMAs, as oil additives,more » effectively reduce the friction coefficient in both mixed and boundary lubrication regimes. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Unfortunately, increased wear rates were observed for these star-shape PAMAs in the boundary lubrication regime suggesting pressure sensitive conformations may exist.« less
  • 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. 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. 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. Whereas poly(n-hexyl methacrylate) hairy NPs cannot be dispersed in PAO under ambient conditions or at 80 °C, interestingly, poly(2-ethylhexyl methacrylate) hairy NPs can be dispersed in PAO at 80 °C but not at room temperature, with a reversible clear-to-cloudy transition observed upon cooling. High-contact-stress ball-on-flat reciprocating sliding tribological tests at 100 °C 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. 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.« less
    Cited by 1
  • 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. 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. 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. Whereas poly(n-hexyl methacrylate) hairy NPs cannot be dispersed in PAO under ambient conditions or at 80 °C, interestingly, poly(2-ethylhexyl methacrylate) hairy NPs can be dispersed in PAO at 80 °C but not at room temperature, with a reversible clear-to-cloudy transition observed upon cooling. High-contact-stress ball-on-flat reciprocating sliding tribological tests at 100 °C 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. 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.« less
    Cited by 1