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@ARTICLE{Dyakonova:280653,
author = {Dyakonova, Margarita A. and Berezkin, Anatoly V. and
Kyriakos, Konstantinos and Gkermpoura, Sandra and Popescu,
Maria T. and Filippov, Sergey K. and Štěpánek, Petr and
Di, Zhenyu and Tsitsilianis, Constantinos and Papadakis,
Christine M.},
title = {{S}alt-{I}nduced {C}hanges in {T}riblock {P}olyampholyte
{H}ydrogels: {C}omputer {S}imulations and {R}heological,
{S}tructural, and {D}ynamic {C}haracterization},
journal = {Macromolecules},
volume = {48},
number = {22},
issn = {1520-5835},
address = {Washington, DC},
publisher = {Soc.},
reportid = {FZJ-2016-00417},
pages = {8177 - 8189},
year = {2015},
note = {FINAL DRAFT POST REFEREE wird nicht zur Verfügung
gestellt, Mic 15.01.2016},
abstract = {We investigate the influence of ionic strength on the
structural properties of stimuli-responsive hydrogels from
triblock polyampholytes PAA-b-P2VP-b-PAA (PAA and P2VP are
negatively charged poly(acrylic acid) and positively charged
poly(2-vinylpyridine)). In our previous studies, we found
that the transition behavior depends on the charge asymmetry
which is controlled by pH and which alters the degree of
ionization of the two types of blocks [Dyakonova
Macromolecules 2014, 47, 7561]. The same triblock
polyampholyte, but with chemically quaternized P2VP (QP2VP)
instead of P2VP as the middle block, is highly positively
charged, independently of pH. In the present investigation,
PAA-b-P2VP-b-PAA at pH 3 and PAA-b-PQ2VP-b-PAA at pH 5 were
chosen to investigate the influence of the ionic strength on
the micellar network morphology by adding NaCl at
concentrations in the physiological range. Computer
simulations of the latter system show that salt addition
results in the formation of larger complexes due to
increased hydrophobicity in the system upon screening of
charges and that the distance between these complexes
increases accordingly. Rheological studies reveal that the
hydrogels from PAA-b-P2VP-b-PAA at pH 3 become softer when
the ionic strength is above 0.10 M. Small-angle neutron
scattering studies have indicated that, in salt-free
solution, both systems form networks. Particularly, it was
found that in PAA-b-PQ2VP-b-PAA, which has a high charge
asymmetry, a variation of the ionic strength leads to
significant changes in network architecture. In contrast, in
PAA-b-P2VP-b-PAA at pD 3, which has a lower charge asymmetry
and the morphology is less sensitive to salt, because the
hydrophobic effect prevails. These findings demonstrate that
the different response of the two systems to the variation
of ionic strength is a consequence of the nature of the
predominant interactions, namely charge screening and
hydrophobic interactions.},
cin = {JCNS (München) ; Jülich Centre for Neutron Science JCNS
(München) ; JCNS-FRM-II / Neutronenstreuung ; JCNS-1},
ddc = {540},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-1-20110106},
pnm = {6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich Centre for
Neutron Research (JCNS) (POF3-623)},
pid = {G:(DE-HGF)POF3-6G15 / G:(DE-HGF)POF3-6G4},
experiment = {EXP:(DE-MLZ)KWS2-20140101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000365463900014},
doi = {10.1021/acs.macromol.5b01746},
url = {https://juser.fz-juelich.de/record/280653},
}