[show abstract][hide abstract] ABSTRACT: The design and construction of a high-performance, low-cost, and easy to assemble adiabatic extension set for homebuilt and commercial spectrometers is described. Described apparatus set was designed for the fast adiabatic passage generation and is based on direct digital synthesizer DDS. This solution gives generator high signal to noise ratio, phase stability even during frequency change which is only possible in expansive commercial high-end hardware. Critical synchronization and timing issues are considered and solutions are discussed. Different experimental conditions and techniques for the measurements are briefly discussed. The proposed system is very flexible and might be used for the measurement of low-frequency nuclear magnetic resonance.
Applied Magnetic Resonance 10/2012; 43(3):331-340. · 0.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: The relation between molecular dynamics and phase properties of the bilayered compound C12H25NH3C1 is studied by differential scanning calorimetry, proton second moment, and spin-lattice relaxation times. In the low-temperature
phase I of the compound methyl and ammonium groups execute a classical threefold reorientation, while the alkylammonium chains
are rigid on the nuclear magnetic resonance time scale. In the intermediate-temperature phase δ a trans-gauche isomerization
of the alkyl chains is observed. In the high-temperature phase α the reorientation of the whole chains about their long axes,
which are parallel to the normal to the ionic layer is evidenced. In the metastable ε phase the dynamics involves classical
rotation of methyl and ammonium groups and CH2 groups motion of the trans-gauche isomerization type.
Applied Magnetic Resonance 04/2012; 19(3):413-420. · 0.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: The paper describes the process of the preparation of new nanocomposites based on poly(butylene terephthalate) and C60 nanoparticles modified by decylamine (DA) and tetracyanoethylene oxide (TCNEO), respectively. Thermal and crystallization properties of new synthesized nanocomposites were investigated by means of thermal differential scanning calorimetry (DSC). The experimental results demonstrate the effect of fullerene derivates, DA-C60 and TCNEO-C60, on the melting and crystallinity processes of nanocomposites. The morphology of new nanocomposites was investigated by SEM.
Journal of Nanomaterials 01/2012; 2012. · 1.55 Impact Factor
[show abstract][hide abstract] ABSTRACT: The solid-state 1H NMR on-resonance and off-resonance techniques have been performed to study molecular dynamics and domain sizes in heterogenous nanocomposites based on poly(butylene terephthalate) and nanoparticles C60 modified by n-decylamine (DA) or tetracyanoethylene oxide (TCNEO), respectively. The spin-lattice off-resonance relaxation times in the rotating frame T1ρoff as well as the second moment M2 of the absorption line were analysed as a function of temperature. To determine the size of heterogeneities and characterize the morphology of the nanocomposites, the 1H NMR spin-diffusion experiment designed by Goldman–Shen [1,2] was performed. The results from the measurements allow us to investigate the spin-diffusion phenomenon and relaxation behavior of the new nanocomposites.
Journal of Non-Crystalline Solids 02/2011; 357(3):1164–1171. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: This paper reports on design and construction of a double coil high-homogeneity ensuring Nuclear Magnetic Resonance Probe for off-resonance relaxation time measurements. NMR off-resonance experiments pose unique technical problems. Long irradiation can overheat the sample, dephase the spins because of B(1) field inhomogeneity and degrade the signal received by requiring the receiver bandwidth to be broader than that needed for normal experiment. The probe proposed solves these problems by introducing a separate off-resonance irradiation coil which is larger than the receiver coil and is wound up on the dewar tube that separates it from the receiver coil thus also thermally protects the sample from overheating. Large size of the irradiation coil also improves the field homogeneity because as a ratio of the sample diameter to the magnet (coil) diameter increases, the field inhomogeneity also increases (Blümich et al., 2008) . The small receiver coil offers maximization of the filling factor and a high signal to the noise ratio.
Journal of Magnetic Resonance 01/2011; 208(1):163-6. · 2.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: Performed analysis of the experimental data obtained from selectively measured proton spin-lattice relaxation times T1 for cyclohexene solutions in carbon tetrachloride at various temperatures is shown to be a method for determining the rotational diffusion coefficients of the molecule, treated as a symmetrical top since Ix ≅ Iy ≠ Iz. The evidenced anisotropy of the rotational motion is of a gas-like nature — the reorientation about the axis of the greatest moment of inertia i. e. the symmetry axis of the diffusion tensor is the slowest and has the largest activation energy. The rotational diffusion model with small-angle reorientations describes adequately the motional behaviour. The values of the rotational diffusion coefficients obtained for the neat liquid at room temperature D‖ = 8.3 · 1010 s−1 and D⟂ = 13.9 · 1010 s−1 are in agreement with calculations based on the modified Nora Hill model.Die durchgeführte Analyse der experimentellen Angaben, die aus selektiv gemessenen Protonen Spin-Gitter-Relaxationszeiten T1 der Zyklohexenlösungen in Kohlenstofftetrachlorid bei verschiedenen Temperaturen erhalten wurden, hat sich gezeigt als eine Methode zur Bestimmung der rotatorischen Diffusionskoeffizienten des Moleküls, das als symmetrischer Kreisel betrachtet wird, da Ix ≅ Iy ≠ Iz. Die festgestellte Anisotropie der Rotationsbewegung ist von gasähnlicher Natur; die Umorientierung um die Achse des größten Inertionsmoments, d. h. die Achse der Symmetrie des Diffusionstensors ist also die langsamste und hat dabei die größte Aktivierungsenergie. Das Modell der rotatorischen Diffusion mit kleinwinkligen Umorientierungen beschreibt adäquat das Bewegungsverhalten. Diffusionskoeffizientenwerte, die für die reine Flüssigkeit bei Zimmertemperatur erhalten wurden, betragen D‖ = 8,3 · 1010 s−1 und D⟂ = 13,9 · 1010 s−1 und sind in Übereinstimmung mit den aufgrund des modifizierten Nora Hill-Modells berechneten Werten.
Berichte der Bunsengesellschaft für physikalische Chemie. 05/2010; 84(8):769 - 775.
[show abstract][hide abstract] ABSTRACT: The relaxation processes as well as the properties of new polymer nanocomposites poly(butylene terephthalate)/decylamine/fullerene have been studied by the 1H nuclear magnetic resonance methods. The correlation times and the activation energies of molecular motions in the nanocomposites were determined. The thermal transitions (glass transition, crystallization and melting events) of these nanocomposites have been investigated by the differential scanning calorimetry (DSC).
Journal of Non-Crystalline Solids 01/2010; 356(11):647-651. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: The frequency dependence of spin–lattice relaxation times measured by means of Fast Field Cycling (FFC) Relaxometry and spin locking on and off-resonance NMR techniques were used to study the molecular dynamics of poly(ethylene oxide) polymer in the confined and bulk phases of PEO/MMT nanocomposite systems. The Rouse model, the renormalized Rouse formalism and the concept of reptation were applied to describe the polymer behavior in the samples studied. The polymer dynamics was found to depend on the molecular weight of the polymer intercalated in the clay structure. Analysis of the NMR T1(ν) profiles allowed discrimination of the molecular dynamics of polymer chains at different locations in the nanocomposite structure.Two components of the T1 spin–lattice relaxation times were indicated for low molecular weight PEO polymers using the FFC method. The longer one was connected with the bulk polymer, whereas the shorter one was attributed to the intercalated polymer fraction. Analysis of the correlation times indicated that polymer confined in montmorillonite galleries is more rigid than that in the bulk phase. To determine the two phases of the polymer for the high molecular weights polymers, additional methods were applied: spin locking, off-resonance NMR techniques and inversion-recovery experiment at a static magnetic field.
Journal of Non-Crystalline Solids 01/2010; · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: The low frequency region in the generalized phonon density of states has been measured for ethisterone by means of neutron scattering. Assignment of the spectral features is facilitated by comparison with results from molecular simulations. The torsional out-of-plane modes of two methyl groups are separated. This finding is consistent with the results of 1H NMR studies.
[show abstract][hide abstract] ABSTRACT: Proton spin-lattice relaxation timesT
1 in 17α hydroxy- and 21 hydroxy-progesterones have been performed in the temperature range from 100 to 400 K at the frequencies
of 30 and 90 MHz. The dynamic processes involving the methyl group reorientation about the threefold symmetry axis of the
C−C bond are separated, and their activation parameters are determined.
Applied Magnetic Resonance 01/2005; 29(2):195-204. · 0.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of the work was to examine molecular dynamics of a series of poly(ethylene 2,6-naphthalate)-polycarbonate blends with
changing weight ratio of copolymers by off-resonance nuclear magnetic resonance technique. It was shown that this technique
provides information about the correlation times of the internal motions. The spectral density function amplitudes were estimated
on the basis of the dispersion of the spin-lattice relaxation time off-resonanceT
lpoff. The measurements were performed for two series of blends which had been injection moulded with and without compatibilizer.
The new polymer materials were also characterized using differential scanning calorimetry. Samples obtained after injection
moulding and annealing became amorphous, which indicates that a reaction of transesterification process between the two polymers
Applied Magnetic Resonance 01/2005; 29(2):221-229. · 0.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: A prototype NMR probe for long RF pulse has been constructed. Its main elements are two coils mounted in the concentric position. The first bigger coil is wound around a glass dewar tube and the second smaller coil is placed inside the dewar. These two coils are thermally isolated by the dewar. A long and strong RF pulse is applied to the bigger coil. The smaller detection coil inside the dewar contains a sample and to this coil a short RF pulse is applied. The two coils are independently tuned and electrically isolated. During the operation of the strong RF pulse the smaller coil has a high resistance to ground (very low Q factor) and does not absorb energy from the bigger coil. During the operation of the short on-resonance RF pulse the bigger coil is detuned to a higher frequency, but the resonance circuit with the small coil is in the electrical resonance. The NMR probe may be used in off-resonance experiments in which long and strong RF pulses are applied to the bigger coil and thereby the problem of the sample overheating is avoided.
Solid State Nuclear Magnetic Resonance 02/2004; 25(1-3):119-24. · 2.10 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of the study was to check the effect of the cation on the molecular dynamics of the anion, which is not directly observed, in different phases of the following compounds: (C4H8NH2)SbCl6(C4H8NH2)Cl, (C4H8NH2)SbCl6 and (4-apyH)ClO4, (4-apyH)SbCl4.
Solid State Nuclear Magnetic Resonance 02/2004; 25(1-3):129-32. · 2.10 Impact Factor
[show abstract][hide abstract] ABSTRACT: Spin-lattice NMR relaxation times T1 in the laboratory frame and T1rho(off) as well as T1rho(off) in the rotating frame off-resonance were employed to the study of molecular dynamics of both pristine PPS and thermally treated poly(p-phenylene sulfide) (PPS). The temperature dependence of T1 was exponential in the whole temperature range studied, whereas T1rho only in low temperatures. In the high temperature range the distribution of relaxation times T1rho and correlation times tau(c) as well as activation energy Ea was observed. The distribution of activation energy determined from T1 minima at 15 and 30 MHz and from low temperature slopes of T1rho dependence as well as from spectral density functions (estimated from proton off-resonance technique) was attributed to the reorientation of phenylene groups around the sulfur-phenyl-sulfur axis in amorphous and crystalline phases of PPS. Furthermore, it is suggested that an additional relaxation mechanism related to interactions of protons with paramagnetic centers is operative in a low temperature range. After thermal treatment of PPS the low temperature minima disappeared and the relaxation times shortened in the low temperature regime. Both these facts were attributed to an increased contribution of spin diffusion in the relaxation process.
Solid State Nuclear Magnetic Resonance 02/2004; 25(1-3):47-52. · 2.10 Impact Factor