TY  - JOUR
A1  - Kind, Lucy
A1  - Plamper, Felix A.
A1  - Goebel, Ronald
A1  - Mantion, Alexandre
A1  - Mueller, Axel H. E.
A1  - Pieles, Uwe
A1  - Taubert, Andreas
A1  - Meier, Wolfgang P.
T1  - Silsesquioxane/polyamine nanoparticle-templated formation of star- or raspberry-like silica nanoparticles
N2  - Silica is an important mineral in biology and technology, and many protocols have been developed for the synthesis of complex silica architectures. The current report shows that silsesquioxane nanoparticles carrying polymer arms on their surface are efficient templates for the fabrication of silica particles with a star- or raspberry-like morphology. The shape of the resulting particles depends on the chemistry of the polymer arms. With poly(N,N- dimethylaminoethyl methacrylate) (PDMAEMA) arms, spherical particles with a less electron dense core form. With poly {[2- (methacryloyloxy)ethyl] trimethylammonium iodide} (PMETAI), star- or raspberry-like particles form. Electron microscopy, electron tomography, and small-angle X-ray scattering show that the resulting silica particles have a complex structure, where a silsequioxane nanoparticle carrying the polymer arms is in the center. Next is a region that is polymer-rich. The outermost region of the particle is a silica layer, where the outer parts of the polymer arms are embedded. Time- resolved zeta-potential and pH measurements, dynamic light scattering, and electron microscopy reveal that silica formation proceeds differently if PDMAEMA is exchanged for PMETAI.
Y1  - 2009
UR  - http://pubs.acs.org/journal/langd5
U6  - https://doi.org/10.1021/La900229n
SN  - 0743-7463
ER  - 
TY  - JOUR
A1  - Mergel, Olga
A1  - Wuennemann, Patrick
A1  - Simon, Ulrich
A1  - Böker, Alexander
A1  - Plamper, Felix A.
T1  - Microgel Size Modulation by Electrochemical Switching
JF  - Chemistry of materials : a publication of the American Chemical Society
N2  - In this work we present the first e-microgel, whose size can be adjusted by application of an electrochemical potential, as seen by dynamic light scattering (3D-DLS in dependence of equilibrium potential) and scanning force microscopy (SFM). Hereby, polyelectrolyte microgels with attracted electroactive counterions provide an effective platform for the manipulation of the microgel size by electrochemical means. The reversible switching of guest molecules, namely, hexacyanoferrates, between oxidized ferricyanide [Fe(CN)(6)](3-) and reduced ferrocyanide [Fe(CN)(6)](4-), influences the cationic host microgel, poly(N-isopropylacrylamide-co-methacrylamidopropyltrimethylammonium chloride) P(NIPAM-co-MAPTAC), and hence the swelling properties of the microgel. The combination of thermo- and redox-responsiveness in one particle leads to a novel type of multistimuli responsive material. In addition, the use of hydrodynamic voltammetry detects directly the preferred uptake of ferricyanide and enables the determination of the nominal charge ratio (ncr) between microgel and entrapped counterions at different states of switching. Further, electrochemical impedance spectroscopy allows a more detailed mechanistic insight into the microgel modulation.
Y1  - 2015
U6  - https://doi.org/10.1021/acs.chemmater.5b02740
SN  - 0897-4756
SN  - 1520-5002
VL  - 27
IS  - 21
SP  - 7306
EP  - 7312
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Wuennemann, Patrick
A1  - Noyong, Michael
A1  - Kreuels, Klaus
A1  - Bruex, Roland
A1  - Gordiichuk, Pavlo
A1  - van Rijn, Patrick
A1  - Plamper, Felix A.
A1  - Simon, Ulrich
A1  - Böker, Alexander
T1  - Microstructured Hydrogel Templates for the Formation of Conductive Gold Nanowire Arrays
JF  - Macromolecular rapid communications
N2  - Microstructured hydrogel allows for a new template-guided method to obtain conductive nanowire arrays on a large scale. To generate the template, an imprinting process is used in order to synthesize the hydrogel directly into the grooves of wrinkled polydimethylsiloxane (PDMS). The resulting poly(N-vinylimidazole)-based hydrogel is defined by the PDMS stamp in pattern and size. Subsequently, tetrachloroaurate(III) ions from aqueous solution are coordinated within the humps of the N-vinylimidazole-containing polymer template and reduced by air plasma. After reduction and development of the gold, to achieve conductive wires, the extension perpendicular to the long axis (width) of the gold strings is considerably reduced compared to the dimension of the parental hydrogel wrinkles (from approximate to 1 mu m down to 200-300 nm). At the same time, the wire-to-wire distance and the overall length of the wires is preserved. The PDMS templates and hydrogel structures are analyzed with scanning force microscopy (SFM) and the gold structures via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy. The conductivity measurements of the gold nanowires are performed in situ in the SEM, showing highly conductive gold leads. Hence, this method can be regarded as a facile nonlithographic top-down approach from micrometer-sized structures to nanometer-sized features.
KW  - 1D structures
KW  - Au nanoarrays
KW  - microgel
KW  - nanoimprint
KW  - lithography
KW  - thin films
Y1  - 2016
U6  - https://doi.org/10.1002/marc.201600287
SN  - 1022-1336
SN  - 1521-3927
VL  - 37
SP  - 1446
EP  - 1452
PB  - Wiley-VCH
CY  - Weinheim
ER  -