Reference : From Molecular Dehydration to Excess Volumes of Phase-Separating PNIPAM Solutions
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Physics
http://hdl.handle.net/10993/16953
From Molecular Dehydration to Excess Volumes of Phase-Separating PNIPAM Solutions
English
Philipp, Martine [Technische Universität München - TUM > Physik Department]
Kyriakos, Konstantinos [Technische Universität München - TUM > Physik Department]
Silvi, Luca [Technische Universität München - TUM > Physik Department, Heinz Maier-Leibnitz Zentrum]
Petry, Winfried [Technische Universität München - TUM > Physik Department, Heinz Maier-Leibnitz Zentrum]
Krüger, Jan-Kristian mailto [University of Luxembourg > Faculty of Science, Technology and Communication (FSTC) > Physics and Materials Science Research Unit >]
Papadakis, Christine [Technische Universität München - TUM > Physik Department]
Mueller-Buschbaum, Peter [Technische Universität München - TUM > Physik Department]
2014
Journal of Physical Chemistry B
American Chemical Society
118
4253-4260
Yes (verified by ORBilu)
International
1520-6106
1520-5207
Washington
DC
[en] For aqueous poly(N-isopropyl acrylamide) (PNIPAM) solutions, a
structural instability leads to the collapse and aggregation of the macromolecules at the
temperature-induced demixing transition. The accompanying cooperative dehydration of
the PNIPAM chains is known to play a crucial role in this phase separation. We elucidate
the impact of partial dehydration of PNIPAM on the volume changes related to the phase
separation of dilute to concentrated PNIPAM solutions. Quasi-elastic neutron scattering
enables us to directly follow the isotropic jump diffusion behavior of the hydration water
and the almost freely diffusing water. As the hydration number decreases from 8 to 2 for
the demixing 25 mass % PNIPAM solution, only a partial dehydration of the PNIPAM
chains occurs. Dilatation studies reveal that the transition-induced volume changes
depend in a remarkable manner on the PNIPAM concentration of the solutions. The
excess volume per mole of H2O molecules expelled from the solvation layers of PNIPAM
during phase separation probably strongly increases from dilute to concentrated PNIPAM
solutions. This finding is qualitatively related to the immense strain-softening previously observed for demixing PNIPAM
solutions.
http://hdl.handle.net/10993/16953
10.1021/jp501539z

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