TY - JOUR
T1 - PMMA- b-PNIPAM Thin Films Display Cononsolvency-Driven Response in Mixed Water/Methanol Vapors
AU - Geiger, Christina
AU - Reitenbach, Julija
AU - Kreuzer, Lucas P.
AU - Widmann, Tobias
AU - Wang, Peixi
AU - Cubitt, Robert
AU - Henschel, Cristiane
AU - Laschewsky, André
AU - Papadakis, Christine M.
AU - Müller-Buschbaum, Peter
N1 - Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/4/13
Y1 - 2021/4/13
N2 - The swelling and solvation of 100-200 nm thin films of a diblock copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N-isopropylacrylamide) (PNIPAM) block are investigated in mixed water/methanol vapors. The processes are followed in real time using spectral reflectance (SR), time-of-flight neutron reflectometry (ToF-NR), and Fourier transform infrared (FT-IR) spectroscopy, applying two neutron scattering contrast variation sequences. After hydration in pure water vapor, the vapor composition (relative to a flow rate of 1 L/min 100%) is changed to 70% water (D2O/H2O) and 30% methanol (CH3OH/CD3OH). Upon the mixed vapor stimulus, a two-step response is found, in which an initially enhanced swelling of the films is followed by a contraction. Differences in the solvent exchange kinetics found in ToF-NR experiments coincide with characteristic changes in the FT-IR spectra. While the initially enhanced swelling of the films is driven by the absorption of methanol, the film contraction is related to the release of both solvents, with almost no further change in solvent composition. In analogy to the coil-to-globule transition encountered in the polymer solution, these film response characteristics are attributed to the cononsolvency behavior of PNIPAM in water/methanol mixtures.
AB - The swelling and solvation of 100-200 nm thin films of a diblock copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N-isopropylacrylamide) (PNIPAM) block are investigated in mixed water/methanol vapors. The processes are followed in real time using spectral reflectance (SR), time-of-flight neutron reflectometry (ToF-NR), and Fourier transform infrared (FT-IR) spectroscopy, applying two neutron scattering contrast variation sequences. After hydration in pure water vapor, the vapor composition (relative to a flow rate of 1 L/min 100%) is changed to 70% water (D2O/H2O) and 30% methanol (CH3OH/CD3OH). Upon the mixed vapor stimulus, a two-step response is found, in which an initially enhanced swelling of the films is followed by a contraction. Differences in the solvent exchange kinetics found in ToF-NR experiments coincide with characteristic changes in the FT-IR spectra. While the initially enhanced swelling of the films is driven by the absorption of methanol, the film contraction is related to the release of both solvents, with almost no further change in solvent composition. In analogy to the coil-to-globule transition encountered in the polymer solution, these film response characteristics are attributed to the cononsolvency behavior of PNIPAM in water/methanol mixtures.
UR - http://www.scopus.com/inward/record.url?scp=85104907747&partnerID=8YFLogxK
U2 - 10.1021/acs.macromol.1c00021
DO - 10.1021/acs.macromol.1c00021
M3 - Article
AN - SCOPUS:85104907747
SN - 0024-9297
VL - 54
SP - 3517
EP - 3530
JO - Macromolecules
JF - Macromolecules
IS - 7
ER -