TY  - JOUR
A1  - Titov, Evgenii
A1  - Sharma, Anjali
A1  - Lomadze, Nino
A1  - Saalfrank, Peter
A1  - Santer, Svetlana
A1  - Bekir, Marek
T1  - Photoisomerization of an azobenzene-containing surfactant within a micelle
JF  - ChemPhotoChem
N2  - Photosensitive azobenzene-containing surfactants have attracted great attention in past years because they offer a means to control soft-matter transformations with light. At concentrations higher than the critical micelle concentration (CMC), the surfactant molecules aggregate and form micelles, which leads to a slowdown of the photoinduced trans -> cis azobenzene isomerization. Here, we combine nonadiabatic dynamics simulations for the surfactant molecules embedded in the micelles with absorption spectroscopy measurements of micellar solutions to uncover the reasons responsible for the reaction slowdown. Our simulations reveal a decrease of isomerization quantum yields for molecules inside the micelles. We also observe a reduction of extinction coefficients upon micellization. These findings explain the deceleration of the trans -> cis switching in micelles of the azobenzene-containing surfactants.
KW  - azobenzene
KW  - micelles
KW  - photoswitches
KW  - rate constants
KW  - surfactants
KW  - surface hopping
Y1  - 2021
U6  - https://doi.org/10.1002/cptc.202100103
SN  - 2367-0932
VL  - 5
IS  - 10
SP  - 926
EP  - 932
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Garnier, Sebastien
A1  - Laschewsky, Andre
T1  - Non-ionic amphiphilic block copolymers by RAFT-polymerization and their self-organization
JF  - Colloid and polymer science : official journal of the Kolloid-Gesellschaft
N2  - Water-soluble, amphiphilic diblock copolymers were synthesized by reversible addition fragmentation chain transfer polymerization. They consist of poly(butyl acrylate) as hydrophobic block with a low glass transition temperature and three different nonionic water-soluble blocks, namely, the classical hydrophilic block poly(dimethylacrylamide), the strongly hydrophilic poly(acryloyloxyethyl methylsulfoxide), and the thermally sensitive poly(N-acryloylpyrrolidine). Aqueous micellar solutions of the block copolymers were prepared and characterized by static and dynamic light scattering analysis (DLS and SLS). No critical micelle concentration could be detected. The micellization was thermodynamically favored, although kinetically slow, exhibiting a marked dependence on the preparation conditions. The polymers formed micelles with a hydrodynamic diameter from 20 to 100 nm, which were stable upon dilution. The micellar size was correlated with the composition of the block copolymers and their overall molar mass. The micelles formed with the two most hydrophilic blocks were particularly stable upon temperature cycles, whereas the thermally sensitive poly(N-acryloylpyrrolidine) block showed a temperature-induced precipitation. According to combined SLS and DLS analysis, the micelles exhibited an elongated shape such as rods or worms. It should be noted that the block copolymers with the most hydrophilic poly(sulfoxide) block formed inverse micelles in certain organic solvents.
KW  - macrosurfactants
KW  - block copolymers
KW  - micelles
KW  - inverse micelles
KW  - sulfoxide
Y1  - 2006
U6  - https://doi.org/10.1007/s00396-006-1484-9
SN  - 0303-402X
VL  - 284
SP  - 1243
EP  - 1254
PB  - Springer
CY  - Berlin
ER  -