TY - JOUR A1 - Arya, Pooja A1 - Jelken, Joachim A1 - Lomadze, Nino A1 - Santer, Svetlana A1 - Bekir, Marek T1 - Kinetics of photo-isomerization of azobenzene containing surfactants JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry N2 - 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. KW - genomic DNA conformation KW - water-interface KW - light photocontrol KW - driven KW - manipulation KW - photoisomerization KW - molecules Y1 - 2020 U6 - https://doi.org/10.1063/1.5135913 SN - 0021-9606 SN - 1089-7690 VL - 152 IS - 2 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Miasnikova, Anna A1 - Benitez-Montoya, Carlos Adrian A1 - Laschewsky, André T1 - Counterintuitive photomodulation of the thermal phase transition of poly(methoxy diethylene glycol acrylate) in aqueous solution by trans-cis isomerization of Copolymerized Azobenzenes JF - Macromolecular chemistry and physics N2 - The non-ionic monomer (methoxy diethylene glycol) acrylate is copolymerized with its azodye-functionalized acrylate analogue using reversible addition-fragmentation chain transfer (RAFT) polymerization. Copolymerization is increasingly difficult with increasing amounts of the azo-dye-bearing monomer. The resulting water-soluble polymers are thermosensitive, exhibiting lower critical solution temperature (LCST) behavior, which can be modulated by the photoinduced trans-cis isomerization of the dye. While already small contents of the hydrophobic azobenzene group reduce the phase-transition temperatures of the copolymers strongly, photoisomerization of the apolar trans-state to the more-polar cis-state has only a small effect, and decreases rather than increases the cloud points. KW - azobenzene KW - photoisomerization KW - statistical copolymers KW - thermoresponsive materials KW - water-soluble polymers Y1 - 2013 U6 - https://doi.org/10.1002/macp.201300203 SN - 1022-1352 VL - 214 IS - 13 SP - 1504 EP - 1514 PB - Wiley-VCH CY - Weinheim ER - TY - GEN A1 - Di Florio, Giuseppe A1 - Bründermann, Erik A1 - Yadavalli, Nataraja Sekhar A1 - Santer, Svetlana A1 - Havenith, Martina T1 - Polarized 3D Raman and nanoscale near-field optical microscopy of optically inscribed surface relief gratings BT - chromophore orientation in azo-doped polymer films N2 - We have used polarized confocal Raman microspectroscopy and scanning near-field optical microscopy with a resolution of 60 nm to characterize photoinscribed grating structures of azobenzene doped polymer films on a glass support. Polarized Raman microscopy allowed determining the reorientation of the chromophores as a function of the grating phase and penetration depth of the inscribing laser in three dimensions. We found periodic patterns, which are not restricted to the surface alone, but appear also well below the surface in the bulk of the material. Near-field optical microscopy with nanoscale resolution revealed lateral two-dimensional optical contrast, which is not observable by atomic force and Raman microscopy. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 247 KW - glass-transition temperature KW - holographic diffraction gratings KW - chain azobenzene polymers KW - molecular-reorientation KW - amorphous polymers KW - data-storage KW - thin-films KW - dye KW - photoisomerization KW - alignment Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95233 SP - 1544 EP - 1554 ER - TY - GEN A1 - Schönborn, Jan Boyke A1 - Hartke, Bernd T1 - Photochemical dynamics of E-methylfurylfulgide BT - kinematic effects on photorelaxation dynamics of furylfulgides N2 - With the present theoretical study of the photochemical switching of E-methylfurylfulgide we contribute an important step towards the understanding of the photochemical processes in furylfulgide-related molecules. We have carried out large-scale, full-dimensional direct semiempirical configuration-interaction surface-hopping dynamics of the photoinduced ring-closure reaction. Simulated static and dynamical UV/Vis-spectra show good agreement with experimental data of the same molecule. By a careful investigation of our dynamical data, we were able to identify marked differences to the dynamics of the previously studied E-isopropylfurylfulgide. With our simulations we can not only reproduce the experimentally observed quantum yield differences qualitatively but we can also pinpoint two reasons for them: kinematics and pre-orientation. With our analysis, we thus offer straightforward molecular explanations for the high sensitivity of the photodynamics towards seemingly minor changes in molecular constitution. Beyond the realm of furylfulgides, these insights provide additional guidance to the rational design of photochemically switchable molecules. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 237 KW - decay dynamics KW - fulgides KW - implementation KW - molecular-dynamics KW - photoinduced nonadiabatic dynamics KW - photoisomerization KW - ring-closure KW - semiempirical methods KW - spectroscopy KW - state Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-94516 SP - 2483 EP - 2490 ER -