0000000001317044
AUTHOR
Robert Graf
Molecular Mobility in Oriented and Unoriented Membranes Based on Poly[2-(Aziridin-1-yl)ethanol]
Unoriented and oriented membranes based on dendronized polymers and copolymers obtained by chemical modification of poly[2-(aziridin-1-yl) ethanol] (PAZE) with the dendron 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy]benzoate were considered. DSC, XRD, CP-MAS NMR and DETA, contribute to characterize the tendency to crystallize, the molecular mobility of the benzyloxy substituent, the dendritic liquid crystalline group and the clearing transition. The orientation of the mesogenic chain somewhat hindered this molecular motion, especially in the full substituted PAZE. The fragility, free volume and thermal expansion coefficients of these membranes near the glass transition are related to the orie…
Free-Standing Mono layer Two-Dimensional Supramolecular Organic Framework with Good Internal Order
Utilizing dynamic self-assembly and self-sorting to obtain large-area, molecularly precise monolayered structures represents a promising approach toward two-dimensional supramolecular organic frameworks (2D SOF) or 2D supramolecular polymers. So far, related approaches suffer from small domain sizes, fragility and weak long-range internal order. Here we report on the self-assembly of a host-guest enhanced donor-acceptor interaction, consisting of a tris(methoxynaphthyl)-substituted truxene spacer, and a naphthalene diimide substituted with N-methyl viologenyl moieties as donor and acceptor monomers, respectively, in combination with cucurbit[8]uril as host monomer toward monolayers of an un…
Temperature‐Responsive Nanoparticles Enable Specific Binding of Apolipoproteins from Human Plasma
Apolipoproteins are an important class of proteins because they provide a so-called stealth effect to nanoparticles. The stealth effect on nanocarriers leads to a reduced unspecific uptake into immune cells and thereby to a prolonged blood circulation time. Herein, a novel strategy to bind apolipoproteins specifically on nanoparticles by adjusting the temperature during their incubation in human plasma is presented. This specific binding, in turn, allows a control of the stealth behavior of the nanoparticles. Nanoparticles with a well-defined poly(N-isopropylacrylamide) shell are prepared, displaying a reversible change of hydrophobicity at a temperature around 32 °C. It is shown by label-f…
Lack of mutagenic and co-mutagenic effects of magnetic fields during magnetic resonance imaging
Mutagenic and co-mutagenic effects of static, pulsed bipolar gradient, and high-frequency magnetic fields, as well as combinations of them, were examined using the Ames test. The Ames test using Salmonella typhimurium bacteria, wild-type strain RTA, preincubation assay, without metabolic activation, was performed. All combinations of magnetic fields were tested with and without co-exposure to N-methyl-N′-nitro-N-nitrosoguanidine and benzo[a]pyrene-4,5-oxide, ethylene oxide, carboplatin, or cisplatin. As expected, chemical mutagens caused a clear-cut increase of the revertants in the Ames test. However, neither the static fields nor a combination of a static magnetic field with the time-vary…
No influence of magnetic fields on cell cycle progression using conditions relevant for patients during MRI.
The purpose of this study was to examine whether exposure to magnetic fields (MFs) relevant for magnetic resonance imaging (MRI) in clinical routine influences cell cycle progression in two tumor cell lines in vitro. HL60 and EA2 cells were exposed to four types of MFs: (i) static MF of 1.5 and 7.05 T, (ii) extremely low frequency magnetic gradient fields (ELFMGFs) with ± 10 mT/m and 100 Hz, as well as ± 100 mT/m and 100 Hz, (iii) pulsed high frequency MF in the radiofrequency (RF) range (63.6 MHz, 5.8 μT), and (iv) a combination of (i–iii). Exposure periods ranged from 1 to 24 h. Cell cycle distribution (G0/G1, S, and G2/M phases) was analyzed by flow cytometry. Cell cycle analysis did not…
Versatile preparation of silica nanocapsules for biomedical applications
Core–shell nanocapsules are receiving increasing interest for drug delivery applications. Silica nanocapsules have been the focus of intensive studies due to their biocompatibility, versatile silica chemistry, and tunable porosity. However, a versatile one-step preparation of silica nanocapsules with well-defined core–shell structure, tunable size, flexible interior loading, and tailored shell composition, permeability, and surface functionalization for site-specific drug release and therapeutic tracking remains a challenge. Herein, an interfacially confined sol–gel process in miniemulsion for the one-step versatile preparation of functional silica nanocapsules is developed. Uniform nanocap…
Solution-processed transparent ferroelectric nylon thin films
We have developed a method to solution process strongly hydrogen-bonded odd nylons into ferroelectric thin films.
Dipolar Relaxation in Functionalized Poly-p-phenylenes Bearing Ultrastrong Dipoles Perpendicular to the Backbone
Local polymer dynamics are studied in polymers bearing dipoles rigidly attached to the backbone. The compounds are based on cyano-substituted dihydrobenzimidazoles bearing ultrastrong dipole moments (∼12 D per repeat unit) incorporated in a poly-p-phenylene backbone, giving rise to polymers with rigid dipoles perpendicular to the chain. They belong to type B polymers according to the Stockmayer classification. They are ideal model systems for studying rotational isomers in the gas phase and the self-assembly and local dynamics in the solid state. Gas phase calculations (DFT) provided the dipole moments, the energetic barriers, and the backbone conformation as a function of the dipole streng…
Stable amorphous calcium oxalate: synthesis and potential intermediate in biomineralization.
Amorphous calcium oxalate nanoparticles with sizes of 10–30 nm were synthesized at room temperature by the hydrolysis of a dimethyl oxalate from ethanol solution.
Synthesis, characterization and fine-tuning of bimodal poly(organosiloxane) nanoparticles
Abstract The acid catalyzed sol–gel type synthesis of polyorganosiloxane core-shell nanoparticles with removable PDMS core in aqueous dispersion leads to the inherent formation of a bimodal size distribution with smaller spheres having approximately 26 nm radii and larger nanoparticles with 60 nm in radius. The origin of the self-organized bimodality is investigated and finally attributed to a combination of stabilization of the growing particles due to i) a miniemulsion-type stabilization by the ultrahydrophobe PDMS and ii) by surface co-stabilization by the employed surfactant. The significant influence of temperature, pH, stirrer speed and amount of the surfactant on the particle sizes a…
CCDC 1814647: Experimental Crystal Structure Determination
Related Article: George Papamokos, Jakob Wudarczyk, Robert Graf, Dieter Schollmeyer, Martin Baumgarten, Klaus Müllen, George Floudas|2018|Macromolecules|51|3330|doi:10.1021/acs.macromol.8b00215
CCDC 1814646: Experimental Crystal Structure Determination
Related Article: George Papamokos, Jakob Wudarczyk, Robert Graf, Dieter Schollmeyer, Martin Baumgarten, Klaus Müllen, George Floudas|2018|Macromolecules|51|3330|doi:10.1021/acs.macromol.8b00215
CCDC 1814648: Experimental Crystal Structure Determination
Related Article: George Papamokos, Jakob Wudarczyk, Robert Graf, Dieter Schollmeyer, Martin Baumgarten, Klaus Müllen, George Floudas|2018|Macromolecules|51|3330|doi:10.1021/acs.macromol.8b00215