Synthesis of estolides from oleic and saturated fatty acids

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Abstract
Oleic acid and various saturated fatty acids, butyric through stearic, were treated with 0.4 equivalents of perchloric acid at either 45 or 55°C to produce complex estolides. Yields varied between 45 and 65% after Kugelrohr distillation. The estolide number (EN), i.e., the average number of fatty acid units added to a base fatty acid, varied as a function of temperature and saturated fatty acid. The shorter‐chain saturated fatty acids, i.e., butyric and hexanoic, provided material with higher degrees of oligomerization (EN=3.31) than stearic acid (EN=1.36). The individual, saturated fatty acid estolides each have very different characteristics, such as color and type of by‐products. The higher‐temperature reactions occurred at faster rates at the expense of yield, and lactones were the predominant side products. At 55°C, lactone yields increased, but the δ‐γ‐lactone ratio decreased; this led to lower estolide yields. The opposite trend was observed for the 45°C reaction. The saturate‐capped, oleic estolides were then esterified with 2‐ethylhexyl alcohol, and the chemical composition of these new estolides remained consistent throughout the course of the reaction.

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