Small-angle neutron scattering from mixtures of sodium dodecyl sulfate and a cationic, bolaform surfactant containing azobenzene

F. Pierce Hubbard, Gabriella Santonicola, Eric W. Kaler, Nicholas L. Abbott

Research output: Contribution to journalArticlepeer-review

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Abstract

This paper reports on the microstructures formed in aqueous solutions containing mixtures of sodium dodecyl sulfate (SDS) and a photosensitive, bolaform surfactant, bis(trimethylammoniumhexyloxy)-azobenzene dibromide (BTHA). By using quasi-elastic light scattering and small-angle neutron scattering, we determined that aqueous solutions containing SDS and the trans isomer of BTHA (0.1 wt % total surfactant, 15 mol % BTHA, 85 mol % SDS) form vesicles with average hydrodynamic diameters of 1350 ± 50 Å and bilayer thicknesses of 35 ± 2 Å. The measured bilayer thickness is consistent with a model of the vesicle bilayer in which the trans isomer of BTHA spans the bilayer. Upon illumination with UV light, the BTHA underwent photoisomerization to produce a cis-rich photostationary state (80% cis isomer). We measured this photoisomerization to drive the reorganization of vesicles into cylindrical aggregates with cross-sectional radii of 19 ± 3 Å and average hydrodynamic diameters of 240 ± 50 Å. Equilibration of the cis-rich solution in the dark at 25 °C for 12 h or illumination of the solution with visible light leads to the recovery of the trans-rich photostationary state of the solution and the reformation of vesicles, thus demonstrating the potential utility of this system as the basis of a tunable fluid.

Original languageEnglish (US)
Pages (from-to)6131-6136
Number of pages6
JournalLangmuir
Volume21
Issue number14
DOIs
StatePublished - Jul 5 2005

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