Synthesis and physical properties of mono-estolides with varying chain lengths

Authors: Cermak, Steven - Steve; Isbell, Terry

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2008
Publication Date: 5/1/2008
Citation: Cermak, S.C., Isbell, T. 2009. Synthesis and physical properties of mono-estolides with varying chain lengths. Industrial Crops and Products. 29(1):205-213.

Interpretive Summary: An understanding of how lubricating oil works in cold weather is of significant importance to the scientific community. As scientists, we must understand the chemistry that takes place to cause molecules to behave as they do; a better understanding will allow chemists to create new products from agricultural sources with superior properties. Thus, we must design experiments so that we can evaluate how well these materials perform. This project investigated a series of compounds called estolides, which have previously proven to be good lubricants, in order to understand what caused them to have outstanding physical properties, in particular a low temperature property called their pour points. There are a number of factors that could affect the physical properties of these lubricants such as: a) what the molecules were made from, b) their chemical structure, and/or c) how they interact with other molecules. A series of different reactions and experiments were developed so that we could produce and test theories of why these compounds display superior low temperature qualities. It was concluded that both the size of and structure of the estolide molecule played a critical role in how well the molecules performed in cold weather applications. By gaining a better understanding of how a molecule behaves under certain conditions, ARS scientists will have the capability to design “smart molecules”. The goal is to design molecules that meet an application versus the old technology of developing an oil and finding applications for the oil.

Technical Abstract: Saturated mono-estolide methyl esters and enriched saturated mono-estolide 2-EH esters were synthesized from oleic and different saturated fatty acids under three different synthetic routes. Estolide numbers (EN), the average number of fatty acid units added to a base fatty acid, varied with synthetic conditions. The attempts at obtaining saturated mono-estolide 2-EH esters, EN = 1, via distillation proved to be challenging, which lead to estolide samples with EN > 1 and the pour point values followed the same trend as the high EN estolides. The other synthetic routes provided saturated mono-estolide methyl esters with EN = 1. The resulting pour point values showed a linear relationship between the saturated capping chain length and pour point. As the saturated capping chain length increased, the pour points also increased (higher temperatures): C-2 capped -30 deg C, C-10 capped -12 deg C, and C-18 capped 3 deg C. The saturated mono-estolide methyl ester viscosities also showed an increase in viscosity at 40 and 100 deg C as the saturated chain lengths increased. The viscosities for the C-4 saturated mono-estolide methyl ester was 9.5 cSt @ 40 deg C and 2.6 cSt @ 100 deg C, while medium chain length derivations (C-10 saturated mono-estolide methyl ester) was 19.7 cSt @ 40 deg C and 4.2 cSt @ 100 deg C, and at the longer chain length derivations (C-18 mono-estolide methyl esters) was 27.6 cSt @ 40 deg C and 10.7 cSt @ 100 deg C. In general, a new series of saturated oleic mono-estolide methyl esters were synthesized and physical properties collected. The physical property data indicated that both chain length and EN affect low temperature properties.