TY  - JOUR
A1  - Ludwig, Michael
A1  - Geisler, Ramsia
A1  - Prévost, Sylvain
A1  - Klitzing, Regine von
T1  - Shape and structure formation of mixed nonionic–anionic surfactant micelles
T2  - Molecules
N2  - 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 (ϕ ≲ 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 (X≈ 0.4–0.6) at which the micelles significantly increase in size and ellipticity due to specific sulfate–EO interactions.
KW  - small-angle neutron scattering
KW  - surfactant
KW  - micelles
KW  - mixed micelles
KW  - Tween20
KW  - polysorbate 20
KW  - BrijL23
KW  - Brij 35
KW  - SDS
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/62200
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-622005
SN  - 1420-3049
VL  - 26
IS  - 14, art. 4136
SP  - 1
EP  - 23
PB  - MDPI
CY  - Basel
ER  -