Surfactants are widely used in various applications ranged from recycling of paper to drug delivery of the current vaccines for covid-19. A collaborative study between the ESS DEMAX team and researchers from Lund university on the behaviour of long-chain alkylglycosides, namely hexadecylmaltoside (C₁₆G₂) shed light on this area by showing how the headgroup anomeric configuration, equatorial (a) or axial (b), strongly influences micelle formation and structure. Small-angle neutron and X-ray scattering revealed that a-C₁₆G₂ forms short cylindrical micelles (contour length ca. 1000 Å), whilst b-C₁₆G₂ assembles into very long worm-like micelles (contour length ca. 10000 Å).¹ This was attributed to the headgroup interactions, where the b configuration prompts a closer monomer-monomer packing as induced by hydrophobic and hydrogen bond interactions. Importantly, we demonstrated that introduction of double bond to the alkyl chain allow these surfactants to form a thermodynamically-stable micellar solution over a wide temperature range.²

In an extension of this work, organic chemist Jia-Fei Poon is synthesising a library of sugar-based surfactants in order to explore how the cis-/trans-configuration and the position of the unsaturation of mono-unsaturated analogues derived from b-C₁₈G₂ (Figure 1) influences the self-assembly and macroscopic response of the system, i.e. the rheology. Understanding the relationship between the physical properties and the chemical structure of these sugar-based surfactants would provide us the knowledge to tailor the properties of these green surfactants for different applications.

¹ J. Larsson, A. Sanchez-Fernandez, A.E. Leung, R. Schweins, B. Wu, T. Nylander, S. Ulvenlund, M. Wahlgren “Molecular structure of maltoside surfactants controls micelle formation and rhelogical behaviour” Journal of Colloid and Interface Science 581, 895-904 (2021) https://doi.org/10.1016/j.jcis.2020.08.116

² J. Larsson, A.E. Leung, C Lang, B. Wu, M. Wahlgren, T. Nylander, S. Ulvenlund, A. Sanchez-Fernandez “Tail unsaturation tailors the thermodynamics and rheology of a self-assembled sugar-based surfactant” Journal of Colloid and Interface Science 585, 178-183 (2021) https://doi.org/10.1016/j.jcis.2020.11.063