Photochemical control of molecular assembly formation in a catanionic surfactant system.
Photochemical control of vesicle disintegration and reformation in aqueous solution was examined using a mixture of 4-butylazobenzene-4'-(oxyethyl)trimethylammonium bromide (AZTMA) as the photoresponsive cationic surfactant and sodium dodecylbenzenesulfonate (SDBS) as the anionic surfactant. Spontaneous vesicle formation was found in a wide-ranging composition of the trans-AZTMA/SDBS system. AZTMA molecules constituting vesicles underwent reversible trans-cis photoisomerization when irradiated with ultraviolet and visible light. Transmission electron microscopy observations using the freeze-fracture technique (FF-TEM) showed that UV light irradiation caused the vesicles to disintegrate into coarse aggregates and visible light irradiation stimulated the reformation of vesicles (normal control). A detailed investigation of the phase state and the effects of UV and visible light irradiation on the AZTMA/SDBS system with the use of electroconductivity, dynamic/static light scattering, and surface tension measurements and FF-TEM observations revealed that in the AZTMA-rich composition (AZTMA/SDBS 9:1) a micellar solution before light irradiation became a vesicular solution after UV light irradiation and visible light irradiation allowed the return to a micellar solution (reverse control). Thus, we could photochemically control the disintegration (normal control) and reformation (reverse control) of vesicles in the same system.
Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Atsutoshi
A
Matsumura
Koji
K
Tsuchiya
Kanjiro
K
Torigoe
Kenichi
K
Sakai
Hideki
H
Sakai
Masahiko
M
Abe
D001391:Azo Compounds / Q000737:chemistry; D008823:Micelles; D044367:Phase Transition / Q000528:radiation effects; D055668:Photochemical Processes; D013237:Stereoisomerism; D013501:Surface-Active Agents / Q000737:chemistry*; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
D001391:Azo Compounds; D008823:Micelles; D013501:Surface-Active Agents; D014867:Water; C009850:azobenzene