TY  - JOUR
A1  - Kyriakos, Konstantinos
A1  - Philipp, Martine
A1  - Lin, Che-Hung
A1  - Dyakonova, Margarita
A1  - Vishnevetskaya, Natalya
A1  - Grillo, Isabelle
A1  - Zaccone, Alessio
A1  - Miasnikova, Anna
A1  - Laschewsky, Andre
A1  - Müller-Buschbaum, Peter
A1  - Papadakis, Christine M.
T1  - Quantifying the Interactions in the Aggregation of Thermoresponsive Polymers: The Effect of Cononsolvency
JF  - Macromolecular rapid communications
N2  - The aggregation kinetics of thermoresponsive core-shell micelles with a poly(N-isopropyl acrylamide) shell in pure water or in mixtures of water with the cosolvents methanol or ethanol at mole fractions of 5% is investigated during a temperature jump across the respective cloud point. Characteristically, these mixtures give rise to cononsolvency behavior. At the cloud point, aggregates are formed, and their growth is followed with time-resolved small-angle neutron scattering. Using the reversible association model, the interaction potential between the aggregates is determined from their growth rate in dependence on the cosolvents. The effect of the cosolvent is attributed to the interaction potential on the structured layer of hydration water around the aggregates. It is surmised that the latter is perturbed by the cosolvent and thus the residual repulsive hydration force between the aggregates is reduced. The larger the molar volume of the cosolvent, the more pronounced is the effect. This framework provides a molecular-level understanding of solvent-mediated effective interactions in polymer solutions and new opportunities for the rational control of self-assembly in complex soft matter systems.
KW  - colloidal aggregation
KW  - cononsolvency
KW  - interaction potential
KW  - polymer solutions
KW  - self-assembled micelles
KW  - thermoresponsive polymers
Y1  - 2016
U6  - https://doi.org/10.1002/marc.201500583
SN  - 1022-1336
SN  - 1521-3927
VL  - 37
SP  - 420
EP  - 425
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Vukicevic, Radovan
A1  - Neffe, Axel T.
A1  - Luetzow, Karola
A1  - Pierce, Benjamin F.
A1  - Lendlein, Andreas
T1  - Conditional Ultrasound Sensitivity of Poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] Microgels for Controlled Lipase Release
JF  - Macromolecular rapid communications
N2  - Triggering the release of cargo from a polymer network by ultrasonication as an external, non-invasive stimulus can be an interesting concept for on-demand release. Here, it is shown that, in pH-and thermosensitive microgels, the ultrasound sensitivity of the polymer network depends on the external conditions. Crosslinked poly[(N-isopropylacrylamide)-co-(vinyl imidazole)] microgels showed a volume phase transition temperature (VPTT) of 25-50 degrees C, which increases with decreasing pH. Above the VPTT the polymer chains are collapsed, while below VPTT they are extended. Only in the case of maximum observed swelling, where the polymer chains are expanded, the microgels are mechanically fragmented through ultrasonication. In contrast, when the polymer chains are partially collapsed it is not possible to manipulate the microgels by ultrasound. Additionally, the ultrasound-induced on-demand release of wheat germ lipase from the microgels could be demonstrated successfully. The principle of conditional ultrasound sensitivity is likely to be general and can be used for selection of matrix-cargo combinations.
KW  - ultrasound
KW  - polymers
KW  - microgels
KW  - lipase release
KW  - controlled release
KW  - thermoresponsive polymers
KW  - biomaterials
Y1  - 2015
U6  - https://doi.org/10.1002/marc.201500311
SN  - 1022-1336
SN  - 1521-3927
VL  - 36
IS  - 21
SP  - 1891
EP  - 1896
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Adelsberger, Joseph
A1  - Metwalli, Ezzeldin
A1  - Diethert, Alexander
A1  - Grillo, Isabelle
A1  - Bivigou Koumba, Achille Mayelle
A1  - Laschewsky, André
A1  - Müller-Buschbaum, Peter
A1  - Papadakis, Christine M.
T1  - Kinetics of collapse transition and cluster formation in a thermoresponsive micellar solution of P(S-b-NIPAM-b-S) induced by a temperature jump
JF  - Macromolecular rapid communications
N2  - Structural changes at the intra- as well as intermicellar level were induced by the LCST-type collapse transition of poly(N-isopropyl acrylamide) in ABA triblock copolymer micelles in water. The distinct process kinetics was followed in situ and in real-time using time-resolved small-angle neutron scattering (SANS), while a micellar solution of a triblock copolymer, consisting of two short deuterated polystyrene endblocks and a long thermoresponsive poly(N-isopropyl acrylamide) middle block, was heated rapidly above its cloud point. A very fast collapse together with a multistep aggregation behavior is observed. The findings of the transition occurring at several size and time levels may have implications for the design and application of such thermoresponsive self-assembled systems.
KW  - polymer physics
KW  - thermoresponsive polymers
KW  - small-angle neutron scattering
KW  - time-resolved measurements
Y1  - 2012
U6  - https://doi.org/10.1002/marc.201100631
SN  - 1022-1336
VL  - 33
IS  - 3
SP  - 254
EP  - 259
PB  - Wiley-Blackwell
CY  - Malden
ER  -