TY  - JOUR
A1  - Ihlenburg, Ramona
A1  - Mai, Tobias
A1  - Thünemann, Andreas F.
A1  - Baerenwald, Ruth
A1  - Saalwächter, Kay
A1  - Koetz, Joachim
A1  - Taubert, Andreas
T1  - Sulfobetaine hydrogels with a complex multilength-scale hierarchical structure
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - Hydrogels with a hierarchical structure were prepared from a new highly water-soluble crosslinker N,N,N',N'-tetramethyl-N,N'-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and from the sulfobetaine monomer 2-(N-3-sulfopropyl-N,N-dimethyl ammonium)ethyl methacrylate. The free radical polymerization of the two compounds is rapid and yields near-transparent hydrogels with sizes up to 5 cm in diameter. Rheology shows a clear correlation between the monomer-to-crosslinker ratio and the storage and loss moduli of the hydrogels. Cryo-scanning electron microscopy, low-field nuclear magnetic resonance (NMR) spectroscopy, and small-angle X-ray scattering show that the gels have a hierarchical structure with features spanning the nanometer to the sub-millimeter scale. The NMR study is challenged by the marked inhomogeneity of the gels and the complex chemical structure of the sulfobetaine monomer. NMR spectroscopy shows how these complications can be addressed via a novel fitting approach that considers the mobility gradient along the side chain of methacrylate-based monomers.
KW  - Defects
KW  - Hydrogels
KW  - Nuclear magnetic resonance spectroscopy
KW  - Scattering
KW  - X-ray scattering
Y1  - 2021
U6  - https://doi.org/10.1021/acs.jpcb.0c10601
SN  - 1520-6106
SN  - 1520-5207
VL  - 125
IS  - 13
SP  - 3398
EP  - 3408
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Fortes Martín, Rebeca
A1  - Thünemann, Andreas F.
A1  - Stockmann, Jörg M.
A1  - Radnik, Jörg
A1  - Koetz, Joachim
T1  - From nanoparticle heteroclusters to filament networks by self-assembly at the water-oil interface of reverse microemulsions
JF  - Langmuir : the ACS journal of surfaces and colloids / American Chemical Society
N2  - Surface self-assembly of spherical nanoparticles of sizes below 10 nm into hierarchical heterostructures is under arising development despite the inherent difficulties of obtaining complex ordering patterns on a larger scale. Due to template-mediated interactions between oil-dispersible superparamagnetic nanoparticles (MNPs) and polyethylenimine- stabilized gold nanoparticles (Au(PEI)NPs) at the water-oil interface of microemulsions, complex nanostructured films can be formed. Characterization of the reverse microemulsion phase by UV-vis absorption revealed the formation of heteroclusters from Winsor type II phases (WPII) using Aerosol-OT (AOT) as the surfactant. SAXS measurements verify the mechanism of initial nanoparticle clustering in defined dimensions. XPS suggested an influence of AOT at the MNP surface. Further, cryo-SEM and TEM visualization demonstrated the elongation of the reverse microemulsions into cylindrical, wormlike structures, which subsequently build up larger nanoparticle superstructure arrangements. Such WPII phases are thus proven to be a new form of soft template, mediating the self-assembly of different nanoparticles in hierarchical network-like filaments over a substrate during solvent evaporation.
KW  - Emulsions
KW  - Liquids
KW  - Nanoparticles
KW  - Water
KW  - X-ray scattering
Y1  - 2021
U6  - https://doi.org/10.1021/acs.langmuir.1c01348
SN  - 0743-7463
VL  - 37
IS  - 29
SP  - 8876
EP  - 8885
PB  - American Chemical Society
CY  - Washington
ER  -