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@PHDTHESIS{Fischer:1010797,
author = {Fischer, Thorsten},
othercontributors = {Möller, Martin and Pich, Andrij},
title = {{C}rosslinked (poly)vinylamine copolymers},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
publisher = {RWTH Aachen University},
reportid = {RWTH-2025-04330},
pages = {1 Online-Ressource : Illustrationen},
year = {2025},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Dissertation, RWTH Aachen University, 2025},
abstract = {This thesis deals mainly with the polymerization of
N-Vinylamides and their subsequent gelation. Therefore, free
amines are generated by hydrolysis of the pre-polymers,
which are subsequently crosslinked by carbonate-based
crosslinkers. Moreover, a method is presented to decorate
inert surfaces with primary amin groups by nitren insertion.
While Gels based on acrylamide, a constitution isomer of
N-vinylformamide (NVF), is subject of manifold literature,
examples of gel systems based on NVF are scarce.
Nevertheless, gel systems based on NVF have the advantage of
a (tailored) number of free primary amine groups via simple
hydrolysis. Primary amine groups can be further
functionalized by numerous reactions to gain specific
properties, e.g. cell binding sequences. Thus, PVAm based
gels can find entrance in medical applications. In general,
the attractiveness of PVAm based systems is caused by the
tailorable number of primary amine groups which in turn
influence properties such as charge density/pH
responsiveness, crosslinking density, hydrophilicity, etc.
However, a direct polymerization to poly(Nvinylamine) (PVAm)
is not possible, since the respective monomer, vinyl amine,
is not stable. Therefore at least two step synthesis is
necessary including a hydrolysis step. In Chapter 2, the
latest methods are summarized to synthesize PVAm, especially
with focus to defined molecular weights and a low
polydispersity index. Moreover, methods are introduced to
obtain thermoresponsive copolymers of polyvinlamide/PVAm. It
is demonstrated how the lower critical solution temperature
(LCST) can be tailored by the molar fraction of VAm or NVF
with different co-monomers. The second part of Chapter 2
deals with the different gelation methods of PVAm. The
synthesis of the gels is on the one hand discussed via an
insitu gelation in the presence of a crosslinker during the
polymerization with subsequent hydrolysis and on the other
hand via the formation of prepolymers which are hydrolyzed
and subsequently crosslinked via the free amine groups.
Furthermore, thermoresponsive gels are presented. In Chapter
3 the copolymerization of NVF with N-vinylacetamide (NVA) is
shown. The copolymerization parameters of both monomers
reveals a statistical distribution. Further show the
kinetics and the selectitivity of the hydrolysis with
respect to NVF and NVA that NVF is hydrolyzed completely
under defined conditions. The amin-functional prepolymers
are crosslinked by phenylcarbonate telechelic poly(ethylene
glycol) (PEG-PC) in presence of a base. The formed hydrogels
are characterized by their swelling ratio and rheological
ixproperties in dependence on the concentration of primary
amines, the concentration of the base, and the concentration
of the crosslinker. It is shown that with this gel system
very high swelling ratios can be realized. In absence of a
base leads the electrostatic interaction between the
urethane groups to physical crosslinking. These are
discussed in Chapter 4. The critical gelation concentration
is determined via rheology. The physical interactions were
examined by NMR and UV-Vis spectroscopy. Furthermore, it is
shown, that the fast gelation leads to inhomogenities, which
could be cured by subsequent heating/cooling cycles as
revealed by a significant increase of the storage modulus. A
possible chemical crosslinking-reaction is ruled out by NMR.
In chapter 5 thermoresponsive copolymers and hydrogels are
prepared. Therefore, NVF is copolymerized with
N-isopropylacrylamide (NIPAm) und subsequently hydrolyzed.
The copolymerization parameters reveal a slightly faster
polymerization of NVF, which means within a polymer chain
there is a gradient from a NVF rich to a NVF poor regime.
NMR shows, that NVF can be selectively hydrolyzed under
defined conditions. The LCST can be tailored via the ratio
of NVF to NIPAm, what is shown in rheology and UV-Vis
spectroscopy. The gelation via
1,2-bis(phenylcarbonate)-ethylene glycol yields in
thermoresponsive hydrogels. These are characterized by NMR,
UV-Vis spectroscopy, and rheology. A two-state model is
applied to describe the phase transition. In Chapter 6 the
surface of chemically inert foils, that means
polymethyl-1-penten (TPX), poly(vinylidene fluorid) (PVDF),
and poly(tetrafluoro ethylene) (PTFE) are functionalized
with a thin hydrogel layer. Therefore a copolymer based on
PVAm is functionalized with Nsuccinimidyl-4-azidotetrafluoro
benzoate. The azide reacts to a highly reactive nitrene
under UV light. These nitrenes can insert in e.g. a C-H bond
leading to a stable covalent binding to the aliphatic and
surprisingly also PTFE surfaces. Thorough investigations of
the wetting behavior of the treated surfaces show, that the
surfaces are hydrophilized. Dynamic contact angle
measurements with the Wilhelmy balance suggest that the
polymerchains can reorientate, which means that the
hydrophobic polymer backbone is directed to the outside
while in contact with air turning to the inside while in
contact with water. This process is reversible.
Consequently, the treated surfaces are amphiphile. This work
might be the base to functionalize chemically inert surfaces
to combine e.g. the mechanical properties of PTFE with cell
recognition sequences, growth factors, drugs, and so on and
so forth.},
cin = {154610 / 150000},
ddc = {540},
cid = {$I:(DE-82)154610_20140620$ / $I:(DE-82)150000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2025-04330},
url = {https://publications.rwth-aachen.de/record/1010797},
}
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