Synthesis and Characterization of Polyethylene Glycol Diesters from Estolides Containing Epoxides and Diols

Estolides from oleic acid, 12‐hydroxystearic acid, and methyl ricinoleate were synthesized and converted to polyethylene glycol (PEG) diesters. Oleic estolide was synthesized from oleic acid as a homo‐oligomeric material using perchloric acid in 68.8% yield and an estolide number (EN) value of 1.29. Estolides from 12‐hydroxystearic acid were homo‐oligomers made by heating under vacuum at 150 °C for 24 hours to give a quantitative yield of estolide with an EN value of 2.55. Oleic acid‐based estolides and 12‐hydroxystearic acid‐based estolide were esterified with PEG‐200 diol to form PEG 200 diesters. Ricinoleate estolides was capped with lauric acid or 12‐hydroxystearic estolide by reacting methyl ricinoleate with the corresponding fatty acids at 150 °C using tin(II) octoate as a catalyst. The corresponding estolides were transesterified with PEG‐200 diol to form the diesters. The residual olefin of ricinoleate was then epoxidized and underwent ring opening hydrolysis to form the corresponding diol. NMR spectroscopy (1H, 13C, distortionless enhancement by polarization transfer, heteronuclear single quantum correlation, heteronuclear multiple bond correlation, and correlated spectroscopy) was used to characterize the products.