TY  - JOUR
A1  - Miasnikova, Anna
A1  - Laschewsky, André
T1  - Influencing the phase transition temperature of poly(methoxy diethylene glycol acrylate) by molar mass, end groups, and polymer architecture
JF  - Journal of polymer science : A, Polymer chemistry
N2  - The easily accessible, but virtually overlooked monomer methoxy diethylene glycol acrylate was polymerized by the RAFT method using monofunctional, difunctional, and trifunctional trithiocarbonates to afford thermoresponsive polymers exhibiting lower critical solution temperature-type phase transitions in aqueous solution. The use of the appropriate RAFT agent allowed for the preparation and systematic variation of polymers with defined molar mass, end-groups, and architecture, including amphiphilic diblock, symmetrical triblock, and triarm star-block copolymers, containing polystyrene as permanently hydrophobic constituent. The cloud points (CPs) of the various polymers proved to be sensitive to all varied parameters, namely molar mass, nature, and number of the end-groups, and the architecture, up to relatively high molar masses. Thus, CPs of the polymers can be adjusted within the physiological interesting range of 2040 degrees C. Remarkably, CPs increased with the molar mass, even when hydrophilic end groups were attached to the polymers.
KW  - water-soluble polymers
KW  - diblock copolymers
KW  - triblock copolymers
KW  - star-block copolymers
KW  - reversible addition fragmentation chain transfer (RAFT)
KW  - LCST
KW  - stimuli-sensitive polymers
Y1  - 2012
U6  - https://doi.org/10.1002/pola.26116
SN  - 0887-624X
VL  - 50
IS  - 16
SP  - 3313
EP  - 3323
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Geiger, Christina
A1  - Reitenbach, Julija
A1  - Henschel, Cristiane
A1  - Kreuzer, Lucas
A1  - Widmann, Tobias
A1  - Wang, Peixi
A1  - Mangiapia, Gaetano
A1  - Moulin, Jean-François
A1  - Papadakis, Christine M.
A1  - Laschewsky, André
A1  - Müller-Buschbaum, Peter
T1  - Ternary nanoswitches realized with multiresponsive PMMA-b-PNIPMAM films in mixed water/acetone vapor atmospheres
JF  - Advanced engineering materials
N2  - To systematically add functionality to nanoscale polymer switches, an understanding of their responsive behavior is crucial. Herein, solvent vapor stimuli are applied to thin films of a diblock copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N-isopropylmethacrylamide) (PNIPMAM) block for realizing ternary nanoswitches. Three significantly distinct film states are successfully implemented by the combination of amphiphilicity and co-nonsolvency effect. The exposure of the thin films to nitrogen, pure water vapor, and mixed water/acetone (90 vol%/10 vol%) vapor switches the films from a dried to a hydrated (solvated and swollen) and a water/acetone-exchanged (solvated and contracted) equilibrium state. These three states have distinctly different film thicknesses and solvent contents, which act as switch positions "off," "on," and "standby." For understanding the switching process, time-of-flight neutron reflectometry (ToF-NR) and spectral reflectance (SR) studies of the swelling and dehydration process are complemented by information on the local solvation of functional groups probed with Fourier-transform infrared (FTIR) spectroscopy. An accelerated responsive behavior beyond a minimum hydration/solvation level is attributed to the fast build-up and depletion of the hydration shell of PNIPMAM, caused by its hydrophobic moieties promoting a cooperative hydration character.
KW  - co-nonsolvency
KW  - diblock copolymers
KW  - nanoswitches
KW  - neutron reflectometry
KW  - thin films
Y1  - 2021
U6  - https://doi.org/10.1002/adem.202100191
SN  - 1438-1656
SN  - 1527-2648
VL  - 23
IS  - 11
PB  - Wiley-VCH
CY  - Weinheim
ER  -