Molecular Dynamics, Dielectric Properties, and Textures of Protonated and Selectively Deuterated 4'-Pentyl-4-biphenylcarbonitrile Liquid Crystal.

Using liquid crystals in near-infrared applications suffers from effects related to processes like parasitic absorption and high sensitivity to UV-light exposure. One way of managing these disadvantages is to use deuterated systems. The combined H and H nuclear magnetic resonance relaxometry method (FFC NMR), dielectric spectroscopy (DS), optical microscopy (POM), and differential scanning calorimetry (DSC) approach was applied to investigate the influence of selective deuteration on the molecular dynamics, thermal properties, self-organization, and electric-field responsiveness to a 4'-pentyl-4-biphenylcarbonitrile (5CB) liquid crystal.

Evidence for NMR Relaxation Enhancement in a Protic Ionic Liquid by the Movement of Protons Independent of the Translational Diffusion of Cations.

The molecular dynamics, thermal stability, and ionic conductivity were studied in the protic ionic liquid 1-methylimidazolium bis(trifluoromethylsulfonyl)imide ([MIm][TFSI]). The relaxation of the H spin-lattice of cations in the measured frequency range (10 kHz to 20 MHz) and temperature (298 to 343 K) is sensitive mainly to slow processes occurring in the molecular dynamics of protic ionic liquid and dominated by the contribution of intermolecular translational diffusion. Molecular rotations give only a constant contribution and become significant in the higher frequency range.

Quantification of manganous ions in wine by NMR relaxometry.

Proton relaxation in model and real wines is investigated for the first time by fast field cycling NMR relaxometry. The relaxation mechanism unambiguously originates form proton interaction with paramagnetic ions naturally present in wines. Profiles of a white Chardonnay wine from Burgundy, a red Medoc, and model wines are well reproduced by Solomon-Bloembergen-Morgan equations.

Effect of gel matrix confinement on the solvent dynamics in supramolecular gels.

Supramolecular gels formed by the sugar gelator of methyl-4,6-O-(p-nitrobenzylidene)-α-d-glucopyranoside (1) with 1,3-propanediol (PG) and 1-butanol (BU) were prepared with different gelator concentrations. The solvent dynamics within gels, characterized by the diffusion coefficient (D) and the spin-lattice relaxation time (T1), was the subject of NMR diffusometry and relaxometry studies. The diffusion was studied as a function of diffusion time and gelator concentrations.

The solvent dynamics at pore surfaces in molecular gels studied by field-cycling magnetic resonance relaxometry.

The molecular dynamics of the solvent molecules at liquid-solid interfaces in low molecular mass gels and in bulk solvents have been identified and characterized with the aid of field-cycling NMR relaxometry. The gels are formed using ethylene glycol (EG) and 1,3-propanediol (PG) with different concentrations of 4,6,4',6'-O-terephthalylidene-bis(methyl α-D-glucopyranoside) (gelator 1). The spin-lattice relaxation times of bulk solvents measured in the function of Larmor frequency were analyzed assuming the intramolecular and intermolecular dipole-dipole interactions.

The solvent-gelator interaction as the origin of different diffusivity behavior of diols in gels formed with sugar-based low-molecular-mass gelator.

Organogels are soft materials consisting of low-molecular-mass gelators (LMOGs) self-assembled through noncovalent interactions into 3D structures, in which free spaces are filled by organic solvents. 4,6,4',6'-O-terephthylidene-bis(methyl-α-d-glucopyranoside) (1) is found to be a new LMOG. It gelatinizes only a limited number of solvents.

Diffusive diffraction phenomenon observed by PGSE NMR technique in a sugar-based low-molecular-mass gel.

The paper presents the diffusive diffraction phenomenon observed by the single-pulse-gradient spin-echo (s-PGSE) NMR technique in a real porous material: a gel composed of low-molecular-mass gelator methyl-4,6-O-(p-nitrobenzylidene)-α-D-glucopyranoside and toluene. Thanks to this phenomenon, we can probe the true microstructure (not xerogel) in which the toluene diffuses. To analyze the measured diffusion-diffraction pattern, we employed a composite bicompartmental model that superimposes restricted diffusion in small cavities of the gel matrix within the bundles of crossing fibers, with free diffusion in large and unconfined compartments between the bundles of crossing fibers.

Morphology, molecular dynamics and electric conductivity of carbohydrate polymer films based on alginic acid and benzimidazole.

The present paper describes a preparation method and molecular investigations of new biodegradable proton-conducting carbohydrate polymer films based on alginic acid and benzimidazole. Electric conductivity was studied in a wide temperature range in order to check the potential application of these compounds as membranes for electrochemical devices. Compared to pure alginic acid powder or its film, the biodegradable film of alginic acid with an addition of benzimidazole exhibits considerably higher conductivity in the range above water boiling temperature (up to approximately 10(-3) S/cm at 473 K).

A possible application of magnetic resonance imaging for pharmaceutical research.

Magnetic resonance imaging (MRI) is a non-destructive and non-invasive method, the experiment can be conducted in situ and allows the studying of the sample and the different processes in vitro or in vivo. 1D, 2D or 3D imaging can be undertaken. MRI is nowadays most widely used in medicine as a clinical diagnostic tool, but has still seen limited application in the food and pharmaceutical sciences.

Evidence of solvent-gelator interaction in sugar-based organogel studied by field-cycling NMR relaxometry.

The dynamics of bulk toluene and toluene confined in the 1,2-O-(1-ethylpropylidene)-α-D-glucofuranose gel was studied using (1)H field-cycling nuclear magnetic resonance relaxometry. The proton spin-lattice relaxation time T(1) was measured as a function of the magnetic field strength and temperature. The observed dispersion in the frequency range 10(4)-10(6) Hz for the relaxation rate of toluene in the gel system give evidence of the interaction between the toluene and the gelator aggregates.

Thermal properties of the gel made by low molecular weight gelator 1,2-O-(1-ethylpropylidene)-alpha-D-glucofuranose with toluene and molecular dynamics of solvent.

The studies of the gel-to-sol phase transition by the Raman, FT-IR, and 1H NMR methods of the gel made by low molecular weight organogelator 1,2-O-(1-ethylpropylidene)-alpha-D-glucofuranose with toluene as the solvent are reported. The FT-IR spectra revealed the existence of a hydrogen bond network formed by gelator molecules in the crystalline and gel phase. In both phases, the network formation is dominated by the gelator self-interaction.

How we can interpret the T1 dispersion of MC, HPMC and HPC polymers above glass temperature?

The chain dynamics in methyl cellulose (MC), hydroxypropylmethyl cellulose (HPMC) and hydroxypropyl cellulose (HPC) were studied with the aid of field-cycling NMR relaxometry technique in the temperature range from 300 to 480 K that is above the glass transition, but below thermal degradation. The frequency dependence of proton spin-lattice relaxation time was determined between 24 kHz and 40 MHz for selected temperatures. The experimental spin-lattice relaxation dispersion data were fitted with the power law relations of T(1) proportional variant omega(gamma) predicted by the tube/reptation model.

Spatially resolved solvent interaction with glassy HPMC polymers studied by magnetic resonance microscopy.

Magnetic resonance microscopy was used to study the interaction of an alkaline water solvent (pH=12) with hydroxypropylmethyl cellulose (HPMC) matrices with different molecular masses Mw=12,000, 86,000, and 120,000. The polymers in the form of cylinders were hydrated at 37 degrees C and monitored at equal time intervals with a 300MHz Bruker AVANCE. The spatially resolved spin-spin relaxations times T2 and diffusion coefficients D of the solvent molecules within the gel layer of HPMC samples, along with changes in the dimension of the glass core of the polymers were determined as a function of hydration times.

The use of the MRI technique in the evaluation of water distribution in tumbled porcine muscle.

The non-destructive magnetic resonance imaging (MRI) technique was used to study the spatial distribution of water in meat samples without and with brine and the influence of injection curing on water distribution in cured meat. Fresh non-treated porcine ham muscles (m. biceps femoris) were used; muscles injected with curing salt and subjected to half-time tumbling (3 h and 20 min) and full-time tumbling (6 h and 40 min) were studied.

Magnetic resonance imaging study of the transport phenomena of solvent into the gel layer of hypromellose matrices containing tetracycline hydrochloride.

Magnetic resonance imaging was used to study the diffusion of a water solution of hydrochloric acid into hypromellose (hydroxypropylmethylcellulose) matrices. Spatially resolved information was obtained about the self-diffusion coefficient and spin-spin relaxation time of solvent protons in the gel layer of hypromellose matrices loaded with different amounts of tetracycline hydrochloride. The data showed the influence of the drug concentration on the diffusion and spin-spin relaxation.

NMR study of molecular dynamics in selected hydrophilic polymers.

The temperature dependencies of the 1H spin-lattice relaxation times T1 and of the proton NMR second moment M2 in the temperature range from about 90 to 420 K were measured for methyl cellulose, hydroxypropyl cellulose and hydroxypropyl methyl cellulose. The proton spin-lattice relaxation measurements reveal two minima due to the C3 reorientation of the methyl groups of the methoxy, methylenemethoxy or propylene oxide groups and the restricted motion of the segment of the polymer chain. The activation energy barriers for these motions were calculated.

The swelling properties of hydroxypropyl methyl cellulose loaded with tetracycline hydrochloride: magnetic resonance imaging study.

Magnetic resonance imaging was used to study the behavior of the gel layer thickness in hydroxypropyl methyl cellulose (HPMC) matrices loaded with different amounts of soluble tetracycline hydrochloride. The time dependence of the diffusion front, effective T2, and proton-density analysis clearly indicates a Case II diffusion mechanism in the system composed of water solution of hydrochloric acid (pH = 2) and HPMC. The solvent penetration front was used to describe the swelling properties as well as the integrity of the HPMC matrices.

In situ, real time observation of the disintegration of paracetamol tablets in aqueous solution by magnetic resonance imaging.

The disintegration behavior of paracetamol tablets was studied by magnetic resonance imaging (MRI) using the Snapshot FLASH method. The total time of the single experiment is 425 ms and allows the study of the disintegration process in real time. The study was carried out in vitro under acidic gastric pH conditions and may help to predict the behavior of paracetamol tablets in the stomach after oral administration.

Magnetic resonance imaging study of the swelling kinetics of hydroxypropylmethylcellulose (HPMC) in water.

Magnetic resonance imaging has been used to monitor the hydration of hydroxypropylmethylcellulose samples by two-dimensional mapping of properties such as spin density and relaxation times. The measurements were performed at two pH values of water: 2 and 6 and two temperatures 25 and 37 degrees C. It is shown that transport behavior of water into HPMC changes from being almost completely relaxation controlled (case II) at pH=2 to Fickian behavior for pH=6.