TY  - JOUR
A1  - Zhong, Qi
A1  - Adelsberger, Joseph
A1  - Niedermeier, M. A.
A1  - Golosova, Anastasi
A1  - Bivigou Koumba, Achille Mayelle
A1  - Laschewsky, André
A1  - Funari, S. S.
A1  - Papadakis, Christine M.
A1  - Müller-Buschbaum, Peter
T1  - The influence of selective solvents on the transition behavior of poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) thick films
JF  - Colloid and polymer science : official journal of the Kolloid-Gesellschaft
N2  - Thick poly(styrene-b-monomethoxydiethylenglycol-acrylate-b-styrene) [P(S-b-MDEGA-b-S)] films (thickness 5 mu m) are prepared from different solvents on flexible substrates by solution casting and investigated with small-angle X-ray scattering. As the solvents are either PS- or PMDEGA-selective, micelles with different core-shell micellar structures are formed. In PMDEGA-selective solvents, the PS block is the core and PMDEGA is the shell, whereas in PS-selective solvents, the order is reversed. After exposing the films to liquid D2O, the micellar structure inside the films prepared from PMDEGA-selective solvents remains unchanged and only the PMDEGA (shell part) swells. On the contrary, in the films prepared from PS-selective solvents, the micelles revert the core and the shell. This reversal causes more entanglements of the PMDEGA chains between the micelles. Moreover, the thermal collapse transition of the PMDEGA block in liquid D2O is significantly broadened. Irrespective of the solvent used for film preparation, the swollen PMDEGA shell does not show a prominent shrinkage when passing the phase transition, and the transition process occurs via compaction. The collapsed micelles have a tendency to densely pack above the transition temperature.
KW  - Hydrogel
KW  - Thin film
KW  - Thermo-responsive
KW  - LCST behavior
KW  - SAXS
Y1  - 2013
U6  - https://doi.org/10.1007/s00396-012-2879-4
SN  - 0303-402X
VL  - 291
IS  - 6
SP  - 1439
EP  - 1451
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Zhong, Qi
A1  - Metwalli, Ezzeldin
A1  - Rawolle, Monika
A1  - Kaune, Gunar
A1  - Bivigou Koumba, Achille Mayelle
A1  - Laschewsky, André
A1  - Papadakis, Christine M.
A1  - Cubitt, Robert
A1  - Müller-Buschbaum, Peter
T1  - Structure and Thermal Response of Thin Thermoresponsive Polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene Films
JF  - Macromolecules : a publication of the American Chemical Society
N2  - Thin thermoresponsive films of the triblock copolymer polystyrene-block-poly(methoxydiethylene glycol acrylate)-block-polystyrene (P(S-b-MDEGA-b-S)) are investigated on silicon substrates. By spin coating, homogeneous and smooth films are prepared for a range of film thicknesses from 6 to 82 nm. Films are stable with respect to dewetting as investigated with optical microscopy and atomic force microscopy. P(S-b-MDEGA-b-S) films with a thickness of 39 nm exhibit a phase transition of the lower critical solution temperature (LCST) type at 36.5 degrees C. The swelling and the thermoresponsive behavior of the films with respect to a sudden thermal stimulus are probed with in-situ neutron reflectivity. In undersaturated water vapor swelling proceeds without thickness increase. The thermoresponse proceeds in three steps: First, the film rejects water as the temperature is above LCST. Next, it stays constant for 600 s, before the collapsed film takes up water again. With ATR-FTIR measurements, changes of bound water in the film caused by different thermal stimuli are studied. Hydrogen bonds only form between C=O and water in the swollen film. Above the LCST most hydrogen bonds with water are broken, but some amount of bound water remains inside the film in agreement with the neutron reflectivity data. Grazing-incidence small-angle X-ray scattering (GISAXS) shows that the inner lateral structure is not significantly influenced by the different thermal stimuli.
Y1  - 2013
U6  - https://doi.org/10.1021/ma400627u
SN  - 0024-9297
VL  - 46
IS  - 10
SP  - 4069
EP  - 4080
PB  - American Chemical Society
CY  - Washington
ER  -