title: Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications.
abstract: We report novel polymeric materials that may be used as viscosity index improvers (VII) for lubricant applications. Our efforts included probing the comb-burst hyper-branched aryl polyester architecture for beneficial viscosity and friction behavior when utilized as an additive in a group I oil. The monomer was designed as to undergo polymerization via polycondensation within the architectural construct (AB2), typical of hyperbranched polymers. The monomer design was comprised of aliphatic arms (12 or 16 methylenes) to provide the necessary lipophilicity to achieve solubility in a non-polar medium. Once polymerized, via catalyst and heat, the surface alcohols were functionalized with fatty acids (lauric and palmitic). Controlling the aliphatic nature of the internal arms and peripheral end-groups provided four unique flexible polymer designs. Changing the reaction time and concentration provided opportunities to investigate the influence of molecular weight and branching density on oil-solubility, viscosity, and friction. Oil-solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on the bulk solution viscosity. At concentrations of 2 wt % in a group I base oil, these polymer additives demonstrated an improved viscosity index and reduced friction coefficient, validating the basic approach.
authors.affiliation: Pacific Northwest National Laboratory, Richland, Washington 99352.
authors.forename: Joshua W
authors.initials: JW
authors.lastname: Robinson
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Pacific Northwest National Laboratory, Richland, Washington 99352.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Bhattacharya
authors.affiliation: Argonne National Laboratory, Lemont, Illinois 60439.
authors.forename: Robert
authors.initials: R
authors.lastname: Erck
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831.
authors.forename: Jun
authors.initials: J
authors.lastname: Qu
authors.affiliation: Pacific Northwest National Laboratory, Richland, Washington 99352.
authors.forename: J Timothy
authors.initials: JT
authors.lastname: Bays
authors.affiliation: Pacific Northwest National Laboratory, Richland, Washington 99352.
authors.forename: Lelia
authors.initials: L
authors.lastname: Cosimbescu