Abstract
The crystal structure development of jojoba-like esters incorporating either 1-decenoic acid and/or 1-decenol, namely octadec-9-enyl dec-9-enoate (JLE-281), and its isomer dec-9-enyl oleate (JLE-282) was investigated to reveal the effect of symmetry about the ester group on crystallization of aliphatic fatty monoesters. The phase transformation path was investigated with temperature-time resolved X-ray diffraction during stepped isothermal crystallization, and while cooling from the melt at a fixed rate. Startling differences in phase behavior were uncovered between the isomers. When stepped isothermals were used, selective extinctions occurred at a transition temperature for JLE-281 but not for JLE-282. The extinctions, which are due to dramatic changes in the electronic density of certain families of planes, indicate a phase transition attributed to a brusque rearrangement of the oxygen atoms in the crystal subcell. The phase transition did not occur when the JLEs were cooled continuously. The crucial role played by the position of the alkyl chain and its orientation relative to the easy rotation site of the C–O bond in the phase trajectories of the JLEs was particularly highlighted.
Highlights
Ester compounds are versatile materials used in many industries
We have recently reported on the synthesis, crystallization and melting behavior, solid content evolution and rheology of three pure jojoba-like esters (JLE) incorporating either 1-decenoic acid and/or 1-decenol and oleic acid and/or oleoyl alcohol, namely octadec-9-enyl dec-9-enoate (JLE-281), dec-9-enyl oleate (JLE-282) and dec-9-enyl dec-9-enoate (JLE-20) [6]. 1-decenoic acid or 1-decenol is a fatty acid/fatty alcohol whose unique terminal double bond structure has not before been investigated in monoester formulations
The phase development of JLE-281 and JLE-282 can be captured by means of conventional X-ray diffraction (XRD) accurately with experiments at the convenient rate of 1 K/min
Summary
Ester compounds are versatile materials used in many industries They possess unique properties suitable for a wide variety of applications ranging from lubricants to cosmetics, medical formulations, and foods [1]. Monoesters, such as those found in jojoba oil, are known to be very functional as lubricants and performance waxes [2,3]. They are a interesting family of compounds which can be exploited to custom design novel functional materials. The effect of structure on their physical properties is poorly understood, hindering our ability to optimize function based on structure
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