Kinetics of photo-isomerization of azobenzene containing surfactants
| Autor: | Marek Bekir, Joachim Jelken, Pooja Arya, Svetlana Santer, Nino Lomadze |
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| Rok vydání: | 2020 |
| Předmět: |
Aqueous solution
010304 chemical physics Photoisomerization Chemistry Institut für Physik und Astronomie General Physics and Astronomy 010402 general chemistry Photochemistry 01 natural sciences Micelle 0104 chemical sciences chemistry.chemical_compound Reaction rate constant Azobenzene Pulmonary surfactant Critical micelle concentration ddc:540 0103 physical sciences ddc:530 Physical and Theoretical Chemistry Isomerization |
| Zdroj: | The Journal of Chemical Physics. 152:024904 |
| ISSN: | 1089-7690 0021-9606 |
| Popis: | We report on photoisomerization kinetics of azobenzene containing surfactants in aqueous solution. The surfactant molecule consists of a positively charged trimethylammonium bromide head group, a hydrophobic spacer connecting via 6 to 10 CH2 groups to the azobenzene unit, and the hydrophobic tail of 1 and 3CH(2) groups. Under exposure to light, the azobenzene photoisomerizes from more stable trans- to metastable cis-state, which can be switched back either thermally in dark or by illumination with light of a longer wavelength. The surfactant isomerization is described by a kinetic model of a pseudo first order reaction approaching equilibrium, where the intensity controls the rate of isomerization until the equilibrated state. The rate constants of the trans-cis and cis-trans photoisomerization are calculated as a function of several parameters such as wavelength and intensity of light, the surfactant concentration, and the length of the hydrophobic tail. The thermal relaxation rate from cis- to trans-state is studied as well. The surfactant isomerization shows a different kinetic below and above the critical micellar concentration of the trans isomer due to steric hindrance within the densely packed micelle but does not depend on the spacer length. |
| Databáze: | OpenAIRE |
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