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@ARTICLE{Lunkad:910196,
author = {Lunkad, Raju and Biehl, Philip and Murmiliuk, Anastasiia
and Blanco, Pablo M. and Mons, Peter and Štěpánek,
Miroslav and Schacher, Felix H. and Košovan, Peter},
title = {{S}imulations and {P}otentiometric {T}itrations {E}nable
{R}eliable {D}etermination of {E}ffective p {K} a {V}alues
of {V}arious {P}olyzwitterions},
journal = {Macromolecules},
volume = {55},
number = {17},
issn = {0024-9297},
address = {Washington, DC},
publisher = {Soc.},
reportid = {FZJ-2022-03676},
pages = {7775 - 7784},
year = {2022},
abstract = {We synthesized three different
polyzwitterions─poly(N,N-diallyl glutamate) (PDAGA),
poly(dehydroalanine) (PDha), and
poly(2-(imidazol-1-yl)acrylic acid) (PImAA)─and
investigated how their ionization states respond to changes
in solution pH. We used molecular simulations to determine
how the net charge per monomer and the ionization states of
individual acidic and basic groups differ from the ideal
(Henderson–Hasselbalch) behavior. To complement the
theoretical predictions, we performed potentiometric
titrations and zeta-potential measurements of all studied
polyzwitterions. By comparing these experiments with
theoretical predictions, we could show that molecular
simulations can predict and explain the origin of the
differences between the effective and bare pKa values of
individual titratable groups. Furthermore, we have shown
that it is not possible to obtain these effective pKa values
directly from the equivalence point recognition criterion
(ERC), commonly used in potentiometric titrations. However,
the effective pKa values can be reliably obtained by
calculating the net charge per monomer from the
potentiometric titration curves and validating these results
against theoretical predictions. The approach we propose
works reliably for polyzwitterions in which the ionization
response is dominated by electrostatic interactions, such as
PDAGA or PDha; however, it fails if other specific
interactions contribute significantly, such as in the case
of PImAA.},
cin = {JCNS-4 / JCNS-FRM-II / MLZ},
ddc = {540},
cid = {I:(DE-Juel1)JCNS-4-20201012 /
I:(DE-Juel1)JCNS-FRM-II-20110218 / I:(DE-588b)4597118-3},
pnm = {6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ)
(POF4-6G4) / 632 - Materials – Quantum, Complex and
Functional Materials (POF4-632)},
pid = {G:(DE-HGF)POF4-6G4 / G:(DE-HGF)POF4-632},
experiment = {EXP:(DE-MLZ)NOSPEC-20140101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000849798100001},
doi = {10.1021/acs.macromol.2c01121},
url = {https://juser.fz-juelich.de/record/910196},
}