Polymeric lubricant additives have been shown to resist the thinning effect of oil with increasing temperature, thereby reducing friction in an engine and improving fuel efficiency for light to medium weight vehicles. Our group is developing novel polymeric materials for this purpose. We are investigating hyperbranched polymers due to their potential to undergo advantageous temperature-dependent conformational changes or intermolecular interactions as part of a lubricant package, sufficient to offset viscosity thinning at increasing temperature. Initial challenges included coping with poor polymer solubility related to numerous polar functional groups found in commercially available hyperbranched polymers, even when modified with long fatty chains to improve solubility. Subsequently, two series of novel comb-burst hyperbranched aryl esters were synthesized, and their properties evaluated with respect to internal chain length, degree of branching, degree of polymerization, molecular weight, and extent of post-modification with fatty acids of varying chain lengths. Solubility was found to decrease with fewer internal carbons, but the number of internal carbons appears to have little influence on bulk solution viscosity. Increased branching and polymerization was found to reduce the solubility of these systems, but it is unclear which parameter (architecture or molecular weight) has the greater impact on viscosity. In concentrations of 1-3 wt %, these polymer additives demonstrated modest improvements to the bulk viscosity of a Group 1 oil, at 40 °C and 100 °C, validating the basic approach. Future work will entail a redesign of our non-linear polymeric additives which will include an increase to the number of peripheral lipophilic moieties, and will target architectures that afford greater temperature dependent hydrodynamic changes within base oils.

Investigations of non-linear polymers as high performance lubricant additives

249th National Meeting (2015)

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