The disclosure generally provides branched diester compounds having exceptional low-temperature and flow properties. The disclosure also provides uses of the branched diester compounds in
lubricant compositions, for example, as a
base oil, and in other applications where their low-temperature and flow properties can be employed beneficially. The disclosure also provides efficient and green methods for making the branched diester compounds.In certain embodiments, a
vegetable oil-based diester (1,6-hexyldioleate) was branched with
propanoic acid (C3) using a green synthetic approach involving
solvent-free and catalyst-free
epoxide ring opening followed by in situ normal esterification. A total of three branched
ester derivatives possessing varied numbers of internal protruding branched ester groups and hydroxyl groups were obtained. All of the pure branched derivatives were comprised of mixtures of positional isomers and / or stereoisomers.
Differential scanning calorimetry (DSC) showed that regardless of the composition inhomogeneity of each branched derivative,
crystallization was suppressed completely in all of the branched compounds, and they all demonstrated glass transitions below −65° C.Without being bound by any theory, it is believed that this unique thermal behavior is attributed to the internal protruding branched moieties and hydroxyl groups, which dramatically slowed down
mass transfer starting with the least branched compound (2-branched derivative). The
viscosity of the branched compounds was one
order of magnitude larger than that of the starting di ester due to the increased branching and increased resistance to flow associated with
hydrogen bonding introduced by the OH groups. Overall, these branched diesters demonstrated superior low temperature and flow properties comparable to existing non-sustainable commercial lubricants and analogous biobased materials which makes them suitable alternatives for use in
lubricant formulations particularly in high performance industrial gear and bearing lubricants.