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@ARTICLE{Raftopoulos:884064,
author = {Raftopoulos, Konstantinos N. and Kyriakos, Konstantinos and
Nuber, Matthias and Niebuur, Bart-Jan and Holderer, Olaf and
Ohl, Michael and Ivanova, Oxana and Pasini, Stefano and
Papadakis, Christine M.},
title = {{C}o-nonsolvency in concentrated aqueous solutions of
{PNIPAM}: effect of methanol on the collective and the chain
dynamics},
journal = {Soft matter},
volume = {16},
number = {36},
issn = {1744-6848},
address = {London},
publisher = {Royal Soc. of Chemistry},
reportid = {FZJ-2020-03073},
pages = {8462-8472},
year = {2020},
abstract = {The polymer dynamics in concentrated solutions of
poly(N-isopropyl acrylamide) (PNIPAM) in D2O/CD3OD mixtures
is investigated in the one-phase region. Two polymer
concentrations (9 and 25 $wt\%)$ and CD3OD contents in the
solvent mixture of 0, 10 and 15 $vol\%$ are chosen.
Temperature-resolved dynamic light scattering (DLS) reveals
the collective dynamics. Two modes are observed, namely the
fast relaxation of polymer segments within the blobs and the
slow collective relaxation of the blobs. As the cloud point
is approached, the correlation length related to the fast
mode increases with CD3OD content. It features critical
scaling behavior, which is consistent with mean-field
behavior for the 9 $wt\%$ PNIPAM solution in pure D2O and
with 3D Ising behavior for all other solutions. While the
slow mode is not very strong in the 9 $wt\%$ PNIPAM solution
in pure D2O, it is significantly more prominent as CD3OD is
added and at all CD3OD contents in the 25 $wt\%$ solution,
which may be attributed to enhanced interaction between the
polymers. Neutron spin-echo spectroscopy (NSE) reveals a
decay in the intermediate structure factor which indicates a
diffusive process. For the polymer concentration of 9
$wt\%,$ the diffusion coefficients from NSE are similar to
the ones from the fast relaxation observed in DLS. In
contrast, they are significantly lower for the solutions
having a polymer concentration of 25 $wt\%,$ which is
attributed to the influence of the dominant large-scale
dynamic heterogeneities. To summarize, addition of cosolvent
leads to enhanced large-scale heterogeneities, which are
reflected in the dynamic behavior at small length scales.},
cin = {JCNS-FRM-II / JCNS-1 / MLZ},
ddc = {530},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-1-20110106 / I:(DE-588b)4597118-3},
pnm = {6215 - Soft Matter, Health and Life Sciences (POF3-621) /
6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich Centre for
Neutron Research (JCNS) (POF3-623)},
pid = {G:(DE-HGF)POF3-6215 / G:(DE-HGF)POF3-6G15 /
G:(DE-HGF)POF3-6G4},
experiment = {EXP:(DE-Juel1)SNS-NSE-20150203 /
EXP:(DE-MLZ)J-NSE-20140101},
typ = {PUB:(DE-HGF)16},
pubmed = {pmid:32856669},
UT = {WOS:000571980300012},
doi = {10.1039/D0SM01007C},
url = {https://juser.fz-juelich.de/record/884064},
}