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  - JOUR
A1  - Weiss, Jan
A1  - Wienk, Hans
A1  - Boelens, Rolf
A1  - Laschewsky, André
T1  - Block copolymer micelles with an intermediate star-/flower-like structure studied by H-1 NMR relaxometry
JF  - Macromolecular chemistry and physics
N2  - H-1 NMR relaxation is used to study the self-assembly of a double thermoresponsive diblock copolymer in dilute aqueous solution. Above the first transition temperature, at which aggregation into micellar structures is observed, the trimethylsilyl (TMS)-labeled end group attached to the shell-forming block shows a biphasic T-2 relaxation. The slow contribution reflects the TMS groups located at the periphery of the hydrophilic shell, in agreement with a star-like micelle. The fast T-2 contribution corresponds to the TMS groups, which fold back toward the hydrophobic core, reflecting a flower-like micelle. These results confirm the formation of block copolymer micelles of an intermediate nature (i.e., of partial flower-like and star-like character), in which a part of the TMS end groups folds back to the core due to hydrophobic interactions.
KW  - block copolymers
KW  - polymer micelles
KW  - relaxation NMR spectroscopy
KW  - self-assembly
KW  - thermoresponsive materials
Y1  - 2014
U6  - https://doi.org/10.1002/macp.201300753
SN  - 1022-1352
SN  - 1521-3935
VL  - 215
IS  - 9
SP  - 915
EP  - 919
PB  - Wiley-VCH
CY  - Weinheim
ER  -