A5052757260- NMR spectroscopy and applications
- Advanced NMR Techniques and Applications
- Material Dynamics and Properties
- Rheology and Fluid Dynamics Studies
- Advanced MRI Techniques and Applications
- Atomic and Molecular Physics
- Innovative Microfluidic and Catalytic Techniques Innovation
- Nanomaterials and Printing Technologies
- Inorganic Fluorides and Related Compounds
- Solid-state spectroscopy and crystallography
- Fluid Dynamics and Thin Films
- Advanced battery technologies research
- Membrane-based Ion Separation Techniques
- Quantum Chromodynamics and Particle Interactions
- Spectroscopy and Quantum Chemical Studies
- Advanced Chemical Physics Studies
- Nanopore and Nanochannel Transport Studies
- Nuclear physics research studies
- Polymer crystallization and properties
- Fuel Cells and Related Materials
- Advanced Neuroimaging Techniques and Applications
- Quantum, superfluid, helium dynamics
- Olfactory and Sensory Function Studies
- Nuclear Physics and Applications
- Force Microscopy Techniques and Applications
Technical University of Darmstadt
2013-2022
Mixtures of protonated and deuterated polybutadiene polydimethylsiloxane are studied by means field-cycling (FC) 1H NMR relaxometry in order to analyze the intra- intermolecular contributions spin–lattice relaxation. They reflect reorientational translational dynamics,respectively. Master curves susceptibility representation χ″(ωτs) constructed employing frequency–temperature superposition with τs denoting segmental correlation time. The contribution is dominating at low frequencies allows...
A recent measurement of the hyperfine splitting in ground state Li-like ${^{208}\mathrm{Bi}}^{80+}$ has established a ``hyperfine puzzle''---the experimental result exhibits $7\ensuremath{\sigma}$ deviation from theoretical prediction [J. Ullmann et al., Nat. Commun. 8, 15484 (2017); J. P. Karr, Phys. 13, 533 (2017)]. We provide evidence that discrepancy is caused by an inaccurate value tabulated nuclear magnetic moment (${\ensuremath{\mu}}_{I}$) $^{209}\mathrm{Bi}$. perform relativistic...
Field-cycling and field-gradient 1H NMR experiments were combined to reveal the segmental mean-square displacement as a function of time for polydimethylsiloxane (PDMS) polybutadiene (PB). Together, more than 10 decades in are covered, all four power-law regimes tube-reptation (TR) model identified with exponents rather close predicted ones. Characteristic polymer properties like tube diameter a0, Kuhn length b, end-to-end distance ⟨R02⟩, correlation τs(T), entanglement τe(T), disengagement...
Water diffusion inside silica pores shows Arrhenius behavior and slows down when the pore diameter decreases or internal ice forms.
The segmental dynamics of 1,4-polybutadiene is investigated by means electronic field cycling 1H NMR. frequency dependence (dispersion) the spin–lattice relaxation time probed over a broad range temperature (223–408 K), molecular mass (355 ≤ M (g/mol) 441 000), and (200 Hz–30 MHz). extremely low frequencies are accessed employing home-built compensation for earth stray fields extending prior reports about 2 decades to lower frequencies. Applying frequency–temperature superposition yields...
We extract the translational diffusion coefficient D(T,M) from field cycling (FC) 1H NMR relaxometry which provides relaxation dispersion of poly(dimethylsiloxane), 1,4-poly(butadiene), poly(styrene), 1,4-poly(isoprene), and poly(propylene glycol) with various molecular masses M. Oligomers very low M, nonentangled (M < Me), entangled > Me) polymers are included. The low-frequency is dominated by dynamics allows extracting D via benefiting an universal power-law characteristic free diffusion....
Due to the single-particle character of quadrupolar interaction in molecular systems, (2)H NMR poses a unique method for probing reorientational dynamics. Spin-lattice relaxation gives access spectral density, and its frequency dependency can be monitored by field-cycling (FC) techniques. However, most FC studies employ (1)H; use is still rare. We report on application investigating dynamics liquids polymers. Commercial as well home-built relaxometers are employed accessing range from 30 Hz...
Field-cycling (FC) 1H and 2H NMR relaxometry is applied to linear polybutadiene (PB) of different molar mass (M) in order test current polymer theories. Applying earth field compensation, five decades the frequency dependence spin–lattice relaxation rate T1–1(ν) = R1(ν) are accessed (200 Hz - 30 MHz), we focus on crossover from Rouse entanglement dynamics. A refined evaluation presented, which avoids application frequency–temperature superposition as well Fourier transformation. Instead,...
We demonstrate that field-cycling 1H NMR relaxometry can be used as a straightforward method of determining translational diffusion coefficient D = D(M) in polymer systems. The spin-lattice relaxation dispersion for polybutadiene different molecular masses M (446 < M/(g mol-1) 9470) is measured at several temperatures (233 T/K 408) broad frequency range. D(T) determined from the intermolecular contribution to overall rate R1(ω), which dominates low-frequency range and follows universal law...
The dynamics of melts linear poly(ethylene-alt-propylene) (PEP) different molar masses (M) is investigated by 1H field-cycling (FC) NMR relaxometry. Employing a commercial and home-built relaxometer the spin-lattice relaxation rate R1(ω) measured in frequency range 200 Hz to 30 MHz temperature 200–400 K. Transforming FC data susceptibility representation applying frequency–temperature superposition, master curves for dipolar correlation function CDD(t/τα) (containing intra- intermolecular...
Proton (1H) field-cycling (FC) NMR relaxometry is applied to monitor the crossover in segmental subdiffusion from Rouse constrained regime an entangled linear polymer melt. The method probes dispersion of spin–lattice relaxation rate R1(ω). Via Fourier transformation mean square displacement ⟨r2(t)⟩ calculated intermolecular contribution R1inter(ω) total 1H As example we chose poly(ethylene propylene) (M = 200k), and singled out by performing isotope dilution experiment. data obtained FC...
We use static field gradient (SFG) NMR to determine the self-diffusion coefficients of protons in fluorine-free sulfonated co-polynaphthoyleneimide (co-PNIS) proton exchange membranes with different ratios hydrophilic hydrophobic groups. The investigations were carried out temperature range from 193 355 K. Because there are not only water but also polymer framework, 1H diffusion studies these may suffer cross-relaxation effects between types protons. To overcome this problem, methods for...
(1)H spin-lattice field cycling relaxation dispersion experiments in the intermediate phase II of solid [C3H5N2]6[Bi4Br18] are presented. Two motional processes have been identified from profiles and quantitatively described. It has concluded that these associated with anisotropic reorientations imidazolium ring, characterized by correlation times order 10(-8) s-10(-9) s about 10(-5) s. Moreover, quadrupole enhancement (QRE) effects originating slowly fluctuating (1)H-(14)N dipolar...
Understanding the evaporation process of binary sessile droplets is essential for optimizing various technical processes, such as inkjet printing or heat transfer. Liquid mixtures whose and wetting properties may differ significantly from those pure liquids are particularly interesting. Concentration gradients occur in these droplets. The challenge to measure concentration without affecting process. Here, spectroscopic methods with spatial resolution can discriminate between components a...
Many technological applications like inkjet printing, coating, or cooling processes rely on the evaporation of sessile droplets. Regarding liquid mixtures, understanding underlying physics is still incomplete and process optimization requires trial error. Our main goal to establish a novel method in this field, one-dimensional magnetic resonance microscopy, investigate binary mixture droplets microliter range. It allows us not only determine droplet volume shape, including contact angle, but...