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

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.
 [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:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0021-8995; VT0604000; CEVT240
Grant/Contract Number:
AC05-00OR22725; AC05-76RL01830; AC02-06CH11357
Accepted Manuscript
Journal Name:
Journal of Applied Polymer Science
Additional Journal Information:
Journal Volume: 133; Journal Issue: 26; Journal ID: ISSN 0021-8995
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)
Country of Publication:
United States