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

Oliver S Hammond; Daniel C Morris; Guillaume Bousrez; Sichao Li; Liliana de Campo; Carl Recsei; Michael Moir; Sergei Glavatskih; Mark W Rutland; Anja-Verena Mudring

doi:10.1021/acssuschemeng.3c04736

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

ACS Sustain Chem Eng. 2024 Jan 22;12(5):1816-1821. doi: 10.1021/acssuschemeng.3c04736. eCollection 2024 Feb 5.

Authors

Oliver S Hammond^{1

2}, Daniel C Morris³, Guillaume Bousrez^{1

2}, Sichao Li⁴, Liliana de Campo⁵, Carl Recsei⁶, Michael Moir⁶, Sergei Glavatskih^{7

8

9}, Mark W Rutland^{4

9

10}, Anja-Verena Mudring^{1

2}

Affiliations

¹ Department of Biological and Chemical Engineering and iNANO, Aarhus University, Aarhus C 8000, Denmark.
² Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 114 18, Sweden.
³ School of Chemical Engineering, University of New South Wales, Sydney 2052, Australia.
⁴ Division of Surface and Corrosion Science, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm 100 44, Sweden.
⁵ Australian Centre for Neutron Scattering, ANSTO, Lucas Heights, New South Wales 2234, Australia.
⁶ National Deuteration Facility, ANSTO, Lucas Heights, New South Wales 2234, Australia.
⁷ Department of Engineering Design, KTH Royal Institute of Technology, Stockholm 100 44, Sweden.
⁸ Department of Electromechanical, Systems and Metal Engineering, Ghent University, Ghent 9052, Belgium.
⁹ School of Chemistry, University of New South Wales, Sydney 2052, Australia.
¹⁰ Laboratoire de Tribologie et Dynamique des Systèmes, École Central de Lyon, Lyon 69130, France.

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.