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Solution Self-Assembly of the Sophorolipid Biosurfactant and Its Mixture with Anionic Surfactant Sodium Dodecyl Benzene Sulfonate

Biomedical Sciences Research Institute Computer Science Research Institute Environmental Sciences Research Institute Nanotechnology & Advanced Materials Research Institute

Penfold, J, Chen, ML, Thomas, RK, Dong, CC, Smyth, TJP, Perfumo, A, Marchant, R, Banat, IM, Stevenson, P, Parry, A, Tucker, I and Grillo, I (2011) Solution Self-Assembly of the Sophorolipid Biosurfactant and Its Mixture with Anionic Surfactant Sodium Dodecyl Benzene Sulfonate. Langmuir, 27 . pp. 8867-8877. [Journal article]

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Abstract

The self-assembly in aqueous solution of the acidic (AS) and lactonic (LS) forms of the sophorolipid biosurfactant, their mixtures, and their mixtures with anionic surfactant sodium dodecyl benzene sulfonate, LAS, has been studied using predominantly small-angle neutron scattering, SANS, at relatively low surfactant concentrations of <30 mM. The more hydrophobic lactonic sophorolipid forms small unilamellar vesicles at low surfactant concentrations, in the concentration range of 0.2 to 3 mM, and transforms via a larger unilamellar vesicle structure at 7mMto a disordered dilute phase of tubules at higher concentrations, 10 to 30 mM. In markedcontrast, the acidic sophorolipid is predominantly in the form of small globular micelles in the concentration range of 0.5 to 30 mM, with a lower concentration of larger, more planar aggregates (lamellar or vesicular) in coexistence. In mixtures of AS and LS, over the same concentration range, the micellar structure associated with the AS sophorolipid dominates themixed-phase behavior. In mixtures of anionic surfactant LAS with the AS sophorolipid, the globular micellar structure dominates over the entire composition and concentration range studied. In contrast, mixtures of LAS with the LS sophorolipid exhibit a rich evolution in phase behavior with solution composition and concentration. At low surfactant concentrations, the small unilamellar vesicle structure present for LS-rich solution compositions evolves into a globular micelle structure as the solution becomes richer in LAS. At higher surfactant concentrations, the disordered lamellar structure present for LS-rich compositions transforms to small vesicle/lamellar coexistence, to lamellar/micellar coexistence, to micellar/lamellar coexistence, and ultimately to a pure micellar phase as the solution becomes richer in LAS. The AS sophorolipid surfactant exhibits self-assembly properties similar to those of most other weakly ionic or nonionic surfactants that have relatively large headgroups. However, the more hydrophobic nature of the lactonic sophorolipid results in a more complex and unusual evolution in phase behavior with concentration and with concentration and composition when mixed with anionic surfactant LAS.

Item Type:Journal article
Faculties and Schools:Faculty of Life and Health Sciences
Faculty of Life and Health Sciences > School of Biomedical Sciences
Research Institutes and Groups:Biomedical Sciences Research Institute
Biomedical Sciences Research Institute > Pharmaceutical Science and Practice
ID Code:21502
Deposited By:Professor Ibrahim Banat
Deposited On:28 Mar 2012 16:23
Last Modified:18 Dec 2012 09:59

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