Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles
Aqueous solutions of a nonionic surfactant (either Tween20 or BrijL23) and an anionic surfactant (sodium dodecyl sulfate, SDS) are investigated, using small-angle neutron scattering (SANS). SANS spectra are analysed by using a core-shell model to describe the form factor of self-assembled surfactant...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-07-01
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| Series: | Molecules |
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| Online Access: | https://www.mdpi.com/1420-3049/26/14/4136 |
| _version_ | 1827687317117075456 |
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| author | Michael Ludwig Ramsia Geisler Sylvain Prévost Regine von Klitzing |
| author_facet | Michael Ludwig Ramsia Geisler Sylvain Prévost Regine von Klitzing |
| author_sort | Michael Ludwig |
| collection | DOAJ |
| description | Aqueous solutions of a nonionic surfactant (either Tween20 or BrijL23) and an anionic surfactant (sodium dodecyl sulfate, SDS) are investigated, using small-angle neutron scattering (SANS). SANS spectra are analysed by using a core-shell model to describe the form factor of self-assembled surfactant micelles; the intermicellar interactions are modelled by using a hard-sphere Percus–Yevick (HS-PY) or a rescaled mean spherical approximation (RMSA) structure factor. Choosing these specific nonionic surfactants allows for comparison of the effect of branched (Tween20) and linear (BrijL23) surfactant headgroups, both constituted of poly-ethylene oxide (PEO) groups. The nonionic–anionic surfactant mixtures are studied at various concentrations up to highly concentrated samples (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ϕ</mi></semantics></math></inline-formula> ≲ 0.45) and various mixing ratios, from pure nonionic to pure anionic surfactant solutions. The scattering data reveal the formation of mixed micelles already at concentrations below the critical micelle concentration of SDS. At higher volume fractions, excluded volume effects dominate the intermicellar structuring, even for charged micelles. In consequence, at high volume fractions, the intermicellar structuring is the same for charged and uncharged micelles. At all mixing ratios, almost spherical mixed micelles form. This offers the opportunity to create a system of colloidal particles with a variable surface charge. This excludes only roughly equimolar mixing ratios (<i>X</i>≈ 0.4–0.6) at which the micelles significantly increase in size and ellipticity due to specific sulfate–EO interactions. |
| first_indexed | 2024-03-10T09:31:47Z |
| format | Article |
| id | doaj.art-c2ccbccab29a4da99a39333a8a970fc3 |
| institution | Directory Open Access Journal |
| issn | 1420-3049 |
| language | English |
| last_indexed | 2024-03-10T09:31:47Z |
| publishDate | 2021-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Molecules |
| spelling | doaj.art-c2ccbccab29a4da99a39333a8a970fc32023-11-22T04:29:09ZengMDPI AGMolecules1420-30492021-07-012614413610.3390/molecules26144136Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant MicellesMichael Ludwig0Ramsia Geisler1Sylvain Prévost2Regine von Klitzing3Soft Matter at Interfaces, Institute for Condensed Matter Physics, Technical University of Darmstadt, D-64289 Darmstadt, GermanySoft Matter at Interfaces, Institute for Condensed Matter Physics, Technical University of Darmstadt, D-64289 Darmstadt, GermanyLarge Scale Structures Group, DS/LSS, Institut Laue-Langevin, CEDEX 9, 38042 Grenoble, FranceSoft Matter at Interfaces, Institute for Condensed Matter Physics, Technical University of Darmstadt, D-64289 Darmstadt, GermanyAqueous solutions of a nonionic surfactant (either Tween20 or BrijL23) and an anionic surfactant (sodium dodecyl sulfate, SDS) are investigated, using small-angle neutron scattering (SANS). SANS spectra are analysed by using a core-shell model to describe the form factor of self-assembled surfactant micelles; the intermicellar interactions are modelled by using a hard-sphere Percus–Yevick (HS-PY) or a rescaled mean spherical approximation (RMSA) structure factor. Choosing these specific nonionic surfactants allows for comparison of the effect of branched (Tween20) and linear (BrijL23) surfactant headgroups, both constituted of poly-ethylene oxide (PEO) groups. The nonionic–anionic surfactant mixtures are studied at various concentrations up to highly concentrated samples (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>ϕ</mi></semantics></math></inline-formula> ≲ 0.45) and various mixing ratios, from pure nonionic to pure anionic surfactant solutions. The scattering data reveal the formation of mixed micelles already at concentrations below the critical micelle concentration of SDS. At higher volume fractions, excluded volume effects dominate the intermicellar structuring, even for charged micelles. In consequence, at high volume fractions, the intermicellar structuring is the same for charged and uncharged micelles. At all mixing ratios, almost spherical mixed micelles form. This offers the opportunity to create a system of colloidal particles with a variable surface charge. This excludes only roughly equimolar mixing ratios (<i>X</i>≈ 0.4–0.6) at which the micelles significantly increase in size and ellipticity due to specific sulfate–EO interactions.https://www.mdpi.com/1420-3049/26/14/4136small-angle neutron scatteringsurfactantmicellesmixed micellesTween20polysorbate 20 |
| spellingShingle | Michael Ludwig Ramsia Geisler Sylvain Prévost Regine von Klitzing Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles Molecules small-angle neutron scattering surfactant micelles mixed micelles Tween20 polysorbate 20 |
| title | Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles |
| title_full | Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles |
| title_fullStr | Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles |
| title_full_unstemmed | Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles |
| title_short | Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles |
| title_sort | shape and structure formation of mixed nonionic anionic surfactant micelles |
| topic | small-angle neutron scattering surfactant micelles mixed micelles Tween20 polysorbate 20 |
| url | https://www.mdpi.com/1420-3049/26/14/4136 |
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