Small-Angle Neutron Scattering Insights into 2-Ethylhexyl Laurate: A Remarkable Bioester

Abstract

Commercial (protiated) samples of the "green" and biodegradable bioester 2-ethylhexyl laurate (2-EHL) were mixed with D-2-EHL synthesized by hydrothermal deuteration, with the mixtures demonstrating bulk structuring in small-angle neutron scattering measurements. Analysis in a polymer scattering framework yielded a radius of gyration (R g ) of 6.5 Å and a Kuhn length (alternatively described as the persistence length or average segment length) of 11.2 Å. Samples of 2-EHL dispersed in acetonitrile formed self-assembled structures exceeding the molecular dimensions of the 2-EHL, with a mean aggregation number (N agg ) of 3.5 ± 0.2 molecules across the tested concentrations. We therefore present structural evidence that this ester can function as a nonionic (co)surfactant. The available surfactant-like conformations appear to enable performance beyond the low calculated hydrophilic−lipophilic balance value of 2.9. Overall, our data offer an explanation for 2-EHL's interfacial adsorption properties via self-assembly, resulting in strong emolliency and lubricity for this sustainable ester-based bio-oil.

Anion Architecture Controls Structure and Electroresponsivity of Anhalogenous Ionic Liquids in a Sustainable Fluid

“…The presence of the solvent-rich outer layer in IL/2-EHL systems studied here can be attributed to the structural characteristics of 2-EHL. Unlike PC, which is a cyclic carbonate ester, 2-EHL features a configuration where the polar ester linkage is partially separated from the apolar alkyl tails, oriented parallel and away from the oxygen-rich “head group”. , This “surfactant-like” structure introduces some degree of self-assembly, or interpenetration, with the [P 6,6,6,14 ] + cation layer through intermolecular interactions with its long alkyl chain, resulting in the formation of the diffuse solvent-rich (secondary) layer. In contrast, the distinct electro-responsive behavior of the ion-rich innermost layer seen in these systems depends on the nature of the specific anion, which will be discussed in more detail below.…”

“…2-Ethylhexyl laurate (H-2-EHL) was obtained commercially as Dehylub 4003 from Emery Oleochemicals GmbH. Perdeuterated 2-ethylhexyl laurate (D-2-EHL) was prepared according to a previously described procedure by the National Deuteration Facility of the Australian Nuclear Science and Technology Organisation (ANSTO) . Both solvents, H/D-2-EHL, were used without further treatment.…”

“…Perdeuterated 2-ethylhexyl laurate (D-2-EHL) was prepared according to a previously described procedure by the National Deuteration Facility of the Australian Nuclear Science and Technology Organisation (ANSTO). 55 Both solvents, H/D-2-EHL, were used without further treatment. Figure 1 illustrates the molecular structure and dimensions of the ILs and 2-EHL.…”

“…These ILs share the same trihexyl­(tetradecyl)­phosphonium ([P 6,6,6,14 ] + ) cation, while the orthoborate-based anions vary between bis­(mandelato)­borate ([BMB] − ), bis­(oxalato)­borate ([BOB] − ), and bis­(salicylato)­borate ([BScB] − ). In comparison to other solvents used in previous studies, such as acetone and propylene carbonate, , 2-EHL is recognized as a green ester-based biodegradable oil, finding practical utility in lubricant formulation due to its low viscosity and high spreading properties. − Moreover, 2-EHL when fully deuterated possesses a high scattering length density (SLD), allowing optimized contrast for SANS and NR measurements. Together, these results establish a clear link between anion architecture and bulk structure as well as their interfacial electroresponsive behavior.…”