Influence of calcium ions on rhamnolipid and rhamnolipid/anionic surfactant adsorption and self-assembly.
The impact of Ca(2+) counterions on the adsorption at the air-water interface and self-assembly in aqueous solution of the rhamnolipid biosurfactant and its mixture with the anionic surfactant sodium dodecylbenzenesulfonate, LAS, has been studied using neutron reflectometry and small-angle neutron s...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
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2013
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| _version_ | 1797082880434765824 |
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| author | Chen, M Dong, C Penfold, J Thomas, R Smyth, T Perfumo, A Marchant, R Banat, I Stevenson, P Parry, A Tucker, I Grillo, I |
| author_facet | Chen, M Dong, C Penfold, J Thomas, R Smyth, T Perfumo, A Marchant, R Banat, I Stevenson, P Parry, A Tucker, I Grillo, I |
| author_sort | Chen, M |
| collection | OXFORD |
| description | The impact of Ca(2+) counterions on the adsorption at the air-water interface and self-assembly in aqueous solution of the rhamnolipid biosurfactant and its mixture with the anionic surfactant sodium dodecylbenzenesulfonate, LAS, has been studied using neutron reflectometry and small-angle neutron scattering. The results illustrate how rhamnolipids are calcium tolerant and how their blending with conventional anionic surfactants improves the calcium tolerance of the anionic surfactant. Ca(2+) has relatively little effect upon the adsorption and self-assembly of the monorhamnose, R1, and dirhamnose, R2, rhamnolipids, even at high pH, due to their predominantly nonionic nature. For R1/R2 mixtures the addition of Ca(2+) has little impact upon the adsorbed amount or the surface composition. For R2/LAS mixtures the addition of Ca(2+) results in an increased adsorption and a surface slightly richer in R2. The weak binding of Ca(2+) to R1 and R2 does result in a change to the degree of ionization of the micelles and especially for mixed R1/R2 micelles at R1-rich solution compositions. The stronger binding of Ca(2+) to LAS results in the addition of Ca(2+) having a much greater impact on the self-assembly of R1/LAS and R2/LAS mixtures. For R1/LAS mixtures the addition of Ca(2+) promotes the formation of more planar structures, even at low surfactant concentrations where in the absence of Ca(2+) mixed globular micelle formation dominates. In R2/LAS mixtures, where there is a greater contrast between the high and low preferred curvatures associated with R2 and LAS, the addition of Ca(2+) results in a more complex evolution in micellar aggregation and the degree of ionization of the micelles. This results in variations in Ca(2+) binding that promotes micellar structures in which a spatial segregation of the two surfactant components within the micelle occurs. |
| first_indexed | 2024-03-07T01:34:09Z |
| format | Journal article |
| id | oxford-uuid:9493d1b2-b592-41ac-b5c4-771c96468ab3 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T01:34:09Z |
| publishDate | 2013 |
| record_format | dspace |
| spelling | oxford-uuid:9493d1b2-b592-41ac-b5c4-771c96468ab32022-03-26T23:40:21ZInfluence of calcium ions on rhamnolipid and rhamnolipid/anionic surfactant adsorption and self-assembly.Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:9493d1b2-b592-41ac-b5c4-771c96468ab3EnglishSymplectic Elements at Oxford2013Chen, MDong, CPenfold, JThomas, RSmyth, TPerfumo, AMarchant, RBanat, IStevenson, PParry, ATucker, IGrillo, IThe impact of Ca(2+) counterions on the adsorption at the air-water interface and self-assembly in aqueous solution of the rhamnolipid biosurfactant and its mixture with the anionic surfactant sodium dodecylbenzenesulfonate, LAS, has been studied using neutron reflectometry and small-angle neutron scattering. The results illustrate how rhamnolipids are calcium tolerant and how their blending with conventional anionic surfactants improves the calcium tolerance of the anionic surfactant. Ca(2+) has relatively little effect upon the adsorption and self-assembly of the monorhamnose, R1, and dirhamnose, R2, rhamnolipids, even at high pH, due to their predominantly nonionic nature. For R1/R2 mixtures the addition of Ca(2+) has little impact upon the adsorbed amount or the surface composition. For R2/LAS mixtures the addition of Ca(2+) results in an increased adsorption and a surface slightly richer in R2. The weak binding of Ca(2+) to R1 and R2 does result in a change to the degree of ionization of the micelles and especially for mixed R1/R2 micelles at R1-rich solution compositions. The stronger binding of Ca(2+) to LAS results in the addition of Ca(2+) having a much greater impact on the self-assembly of R1/LAS and R2/LAS mixtures. For R1/LAS mixtures the addition of Ca(2+) promotes the formation of more planar structures, even at low surfactant concentrations where in the absence of Ca(2+) mixed globular micelle formation dominates. In R2/LAS mixtures, where there is a greater contrast between the high and low preferred curvatures associated with R2 and LAS, the addition of Ca(2+) results in a more complex evolution in micellar aggregation and the degree of ionization of the micelles. This results in variations in Ca(2+) binding that promotes micellar structures in which a spatial segregation of the two surfactant components within the micelle occurs. |
| spellingShingle | Chen, M Dong, C Penfold, J Thomas, R Smyth, T Perfumo, A Marchant, R Banat, I Stevenson, P Parry, A Tucker, I Grillo, I Influence of calcium ions on rhamnolipid and rhamnolipid/anionic surfactant adsorption and self-assembly. |
| title | Influence of calcium ions on rhamnolipid and rhamnolipid/anionic surfactant adsorption and self-assembly. |
| title_full | Influence of calcium ions on rhamnolipid and rhamnolipid/anionic surfactant adsorption and self-assembly. |
| title_fullStr | Influence of calcium ions on rhamnolipid and rhamnolipid/anionic surfactant adsorption and self-assembly. |
| title_full_unstemmed | Influence of calcium ions on rhamnolipid and rhamnolipid/anionic surfactant adsorption and self-assembly. |
| title_short | Influence of calcium ions on rhamnolipid and rhamnolipid/anionic surfactant adsorption and self-assembly. |
| title_sort | influence of calcium ions on rhamnolipid and rhamnolipid anionic surfactant adsorption and self assembly |
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