scholarly journals The Water Polymorphism and the Liquid–Liquid Transition from Transport Data

Physchem ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 202-214
Author(s):  
Francesco Mallamace ◽  
Domenico Mallamace ◽  
Giuseppe Mensitieri ◽  
Sow-Hsin Chen ◽  
Paola Lanzafame ◽  
...  
Keyword(s):  
Specific Heat ◽  
Relaxation Times ◽  
Configurational Entropy ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Glass Forming ◽  
T1 Relaxation ◽  
Liquid Transition ◽  
Measured Water ◽  
Supercooled Region

NMR spectroscopic literature data are used, in a wide temperature-pressure range (180–350 K and 0.1–400 MPa), to study the water polymorphism and the validity of the liquid–liquid transition (LLT) hypothesis. We have considered the self-diffusion coefficient DS and the reorientational correlation time τθ (obtained from spin-lattice T1 relaxation times), measured, respectively, in bulk and emulsion liquid water from the stable to well inside the metastable supercooled region. As an effect of the hydrogen bond (HB) networking, the isobars of both these transport functions evolve with T by changing by several orders of magnitude, whereas their pressure dependence become more and more pronounced at lower temperatures. Both these transport functions were then studied according to the Adam–Gibbs model, typical of glass forming liquids, obtaining the water configurational entropy and the corresponding specific heat contribution. The comparison of the evaluated CP,conf isobars with the experimentally measured water specific heat reveals the full consistency of this analysis. In particular, the observed CP,conf maxima and its diverging behaviors clearly reveals the presence of the LLT and with a reasonable approximation the liquid–liquid critical point (LLCP) locus in the phase diagram.

NMR Imaging Studies of Vulcanized Butyl Rubber

1991 ◽  
Vol 64 (4) ◽  
pp. 635-640 ◽  
Author(s):  
M. R. Krejsa ◽  
J. L. Koenig
Keyword(s):  
Crosslink Density ◽  
Relaxation Times ◽  
Nmr Imaging ◽  
Thermal Gradients ◽  
Chemical Probes ◽  
Imaging Studies ◽  
Spin Lattice ◽  
T1 Relaxation ◽  
Entrapped Air ◽  
Effects Of Aging

Abstract NMR imaging is a useful technique for studying the physical and spatial microstructure of cured elastomers. Different swelling agents can be used as chemical probes to detect varying amounts of microstructural differences. Imaging can be used to detect highly cured regions due to aging, poor mixing, and thermal gradients. NMRI is thus useful to study spatial distribution of crosslinks and is sensitive to changes in this distribution of crosslinks due to thermal gradients and the effects of aging and reversion processes. It can also be used to observed entrapped air in air-aged samples. Spin-lattice T1, relaxation times for solvent in cured elastomers have been shown to be shorter than the bulk solvent T1 values, providing a new method for determining the crosslink density. NMRI results have suggested that cure reversion and postcuring processes produce similar spatial results.

scholarly journals 15N and 133Cs Solid NMR Studies on Ionic Dynamics in Plastic CsNO2

1996 ◽  
Vol 51 (5-6) ◽  
pp. 761-768 ◽  
Author(s):  
H. Honda ◽  
M. Kenmotsu ◽  
N. Onoda-Yamamuro ◽  
H. Ohki ◽  
S. Ishimaru ◽  
...  
Keyword(s):  
Phase Ii ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Temperature Phase ◽  
Nmr Studies ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Solid Nmr ◽  
Plastic Phase

The temperature dependence of the 15N and 133Cs NMR spin-lattice relaxation times, the 15N spin-spin relaxation time, and the 15N and 133Cs spectra of CsNO2 was observed in the plastic phase (209.2 < T < 673 K (m. p.)) and the low-temperature phase (Phase II). In Phase II we found the NO-2 180°-flip, which could be attributed to the anomalous increase of the heat capacity curve, and determined the activation energy of this motion to be 8.7-11.7 kJ mol-1. The 15N and 133Cs spectra in this phase are inconsistent with the reported crystal structure R3̅m and can be explained by lower crystal symmetry. In the plastic phase we detected a new anionic motion with 11 kJ mol-1 , an isotropic NO-2 reorientation with 8.5-9 kJ mol-1, and ionic self-diffusion with 47 kJ mol-1. The presence of ionic self-diffusion was confirmed by measuring the electrical conductivity.

Ionic Dynamics in LiNO2 Studied by 7Li and 15N Solid NMR

1999 ◽  
Vol 54 (8-9) ◽  
pp. 519-523 ◽  
Author(s):  
Hisashi Honda ◽  
Shin'ich Ishimaru ◽  
Ryuichi Ikeda
Keyword(s):  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
The Self ◽  
Spin Lattice Relaxation ◽  
Plastic Crystal ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Solid Nmr ◽  
Temperature Dependences

The temperature dependences of 7Li and 15N NMR spin-lattice relaxation times and spectra in LiNO2 were measured in the range 120 K -473 K (m.p.). The 180°-flip motion of NO2-- ions along or perpendicular to the molecular C2 -axis and the self-diffusion of Li+ ions (activation energies of 42 -44 and 100 kJ mol-1 , respectively) were observed in this range. From the comparison of the observed activation parameters with those reported for plastic phases of alkali metal nitrites, a new characteristic of the plastic crystal was obtained.

scholarly journals Proton Magnetic Resonance Studies of Water in Slime Mould Plasmodia

1971 ◽  
Vol 24 (3) ◽  
pp. 497 ◽  
Author(s):  
JA Walter ◽  
AB Hope
Keyword(s):  
Relaxation Times ◽  
Bulk Water ◽  
Proton Spin ◽  
Water Molecules ◽  
Signal Pulse ◽  
Cellular Functions ◽  
Slime Mould ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Cytoplasmic Structures

Steady-state and pulse n.m.r. techniques have been applied in a study of water in the cytoplasm of slime mould plasmodia (Ph;ysarum polycephalum). The former method has been used to confirm that the signal detected was from protons in water molecules, and to estimate the fraction of the total water in the sample that was contributing to the observed signal. Pulse techniques have enabled direct measurement of the self-diffusion coefficient D of the bulk water in the cytoplasm, and the proton spin-lattice and spin-spin relaxation times Tl and T2 respectively. The measurements of D can be accounted for if most of the water is in a "free" state, similar to water in a dilute ionic solution, but with a lower value of D due to the obstruction effect of macromolecules and cytoplasmic structures. The values of Tl and T2 indicate that a small "bound" fraction of the water molecules has more restricted motion. The assumption of a two-state model, with exchange of water molecules between "free" and "bound" phases in a time ~ 10-3 sec, yields a representative correlation time T "'" 10-8 sec for the bound fraction. This model is the simplest compatible with all the above results. The underlying assumptions, the extent to which it is likely to be an approximation, and the implications regarding some theories of cellular functions are discussed. Similar results have also been obtained from samples of toad leg muscle, ceils from the meristematic region of pea roots, and from agar and gelatin gels.

Ionic Dynamics in Plastic Crystal KNO2 Studied by 39K and 15N NMR

1994 ◽  
Vol 49 (1-2) ◽  
pp. 247-252 ◽  
Author(s):  
Motoko Kenmotsu ◽  
Hisashi Honda ◽  
Hiroshi Ohki ◽  
Ryuichi Ikeda ◽  
Tomoki Erata ◽  
...  
Keyword(s):  
Intermediate Phase ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
15N Nmr ◽  
Temperature Phase ◽  
Self Diffusion ◽  
Spin Lattice

AbstractThe spin-lattice relaxation time of 39K NMR observed in the low-temperature phase (T<264.1 K) of KNO2 is explained by the quadrupole mechanism contributed from a newly found NO2- motion. The in-plane C3 reorientation and the overvall NO2 rotation as well as the self-diffusion were shown in the intermediate phase (T ≤ 314.7 K) and the high-temperature plastic phase (T < melting point: 710 K), respectively, by observing 39K and 15N NMR relaxation times and 15N lineshapes.

Molecular Motion in Solid Tetrabutylammonium Iodide

1987 ◽  
Vol 42 (3) ◽  
pp. 253-257 ◽  
Author(s):  
Barbara Szafrańska ◽  
Zdzisław Pająk
Keyword(s):  
Molecular Motion ◽  
Structural Phase ◽  
Relaxation Times ◽  
Activation Parameters ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Self Diffusion ◽  
Spin Lattice ◽  
Tetrabutylammonium Iodide

The temperature dependence of the 1H second moment and the T1 and T1ϱ spin-lattice relaxation times obtained for polycrystalline tetrabutylammonium iodide are interpreted in terms of the C3 methyl group reorientation appearing together with cationic tumbling for which the activation parameters have been determined. IR spectra point to the existence of weak C - H . . . I hydrogen bonds. A structural phase transition evidenced at about 386 K is found to be related to the onset of cationic self-diffusion.

scholarly journals Micro DSC and NMR MOUSE studies of collagen–vegetable tannin interaction mechanism during leather making

2020 ◽  
Author(s):  
Claudiu Sendrea ◽  
Maria-Cristina Micu ◽  
Emanuel Hadimbu ◽  
Simona Maria Paunescu ◽  
Iulia Maria Caniola ◽  
...  
Keyword(s):  
Relaxation Times ◽  
Water Environment ◽  
Interaction Mechanism ◽  
High Sensitivity ◽  
Collagen Matrix ◽  
Spin Lattice ◽  
Dsc Measurements ◽  
T1 Relaxation ◽  
Micro Dsc ◽  
Portable Nmr

In this study NMR MOUSE and micro DSC techniques were used to investigate the interaction between collagen and various vegetable tannins during leather making process with the aim of gaining a deeper understanding of different water environment in relation to tannin type. We have previously showed that relaxation times may provide useful information on collagen matrix properties. The vegetable tanned leathers were obtained by patented techniques inspired from ancient recipes at the National R&D Institute for Textile and Leather, ICPI Division, Bucharest using various vegetable extracts such as myrobalan, gambier and chestnut. Longitudinal and transversal relaxation times T1 and T2eff were measured using a PM2 portable NMR-MOUSE with 20.05 MHz frequency. Micro DSC measurements were carried out with a high-sensitivity SETARAM Micro-DSC III in the temperature range (5 to 95) °C at 0.5 K min-1 heating rate. The investigated leathers showed significant differences in the values of spin-spin (T2eff) and spin-lattice (T1) relaxation times depending on tannin type that well corelates with the variation of the calorimetric parameters (denaturation temperature and enthalpy, peak shape). These results highlight the complementarity of the information obtained by the two techniques and open new ways for both designing new leather assortments and analyses of historical and archaeological leather.

Sign in / Sign up

Export Citation Format

Share Document