Download or read book Room Temperature and High Temperature 31P Solid state Nuclear Magnetic Resonance Studies of Metal Selenophosphate and K P Se Flux Reactions written by Christian G. Canlas and published by . This book was released on 2004 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Solid state Nuclear Magnetic Resonance Spectroscopy of Phosphazene Polymers written by Alexey S. Borisov and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High-resolution one-dimensional 1H, 19F, 31P and 13C MAS NMR experiments were used in a morphological study of solvent-cast and heat-treated poly[bis(trifluoroethoxy)phosphazene] (PBFP). Deconvolution analyses performed on all Nuclear Magnetic Resonance (NMR) spectra are presented. These results suggest the presence of broad and narrow overlapping components at ambient temperature, which were assigned to the crystalline, amorphous and the mesophase regions within the polymer, respectively. The number of signals in the spectra was independently verified using 1H, 19F and 13C Discrimination Induced by Variable Amplitude Minipulses (DIVAM) nutation experiments. Deconvolution analyses showed that heat-treatment increases the overall crystallinity of the solvent-cast PBFP. Further studies conducted on two preparations of the polymer showed significant differences in crystallinity due to variations in the reaction conditions. Magic-Angle Spinning (MAS) NMR spectra of PBFP obtained via living cationic polymerization at ambient temperature indicated that the polymer contains mostly amorphous and mesophase regions with only a small contribution from the crystalline domain. Variable-temperature 31P NMR experiments suggested that the thermotropic transition occurs in a temperature range of 80oC to 90oC, where the crystalline signal disappears and a new signal due to a liquid crystalline phase emerges. Spin-lock 31P experiments provided rates of the transverse relaxation in the rotating frame for each signal, showing that the crystalline and the amorphous regions within the polymer are characterized by significantly different mobilities at ambient temperatures, while the v comparable degree of motion occurs between the amorphous and mesophase environments at temperatures above 90oC. The process of thermal ring-opening polymerization of hexachlorocyclotriphosphazene was monitored using one-dimensional 31P MAS NMR at different stages of the reaction. The ratio between cyclic species and the high molecular weight poly(dichlorophosphazene) was seen to change over time. 31P NMR was seen to be a potentially valuable tool in monitoring rates of chain propagation, branching and cross-linking. Two-dimensional 31P homonuclear Radio-Frequency Driven Recoupling (RFDR) and Incredible Natural Abundance Double Quantum Transfer (INADEQUATE) MAS NMR experiments were first tested on the partially phenoxy-substituted hexachlorocyclotriphosphazene, and subsequently applied in the study of a preparation of the partially trifluoroethoxy-substituted poly(dichlorophosphazene). Very high resolution was obtained in the direct dimension due to the presence of low molecular weight species. Preliminary spectral assignments of all of the observed signals were made on the basis of both known chemical shifts of the related species, and the through-space and through-bond phosphorous-phosphorous connectivities.
Download or read book Handbook of Phosphorus 31 Nuclear Magnetic Resonance Data 1990 written by John C. Tebby and published by CRC Press. This book was released on 2017-11-22 with total page 1140 pages. Available in PDF, EPUB and Kindle. Book excerpt: To fully utilize Nuclear Magnetic Resonance (NMR) spectroscopy, a comprehensive and well-organized compilation of NMR data is necessary. While compilations have been available for other important NMR nuclei, such as carbon and fluorine, no comprehensive collection of data has been prepared for phosphorus-until now. The CRC Handbook of Phosphorus-31 Nuclear Magnetic Resonance Data provides a collection of 31P NMR chemical shifts for nearly 20,000 organic and inorganic phosphorus compounds. Each class of phosphorus compound is discussed. Bond types, stereochemistry (with the exception of metal complexes), media, important coupling constants, and data sources are included. The information is systematically organized according to coordination state, the atoms bound to phosphorus, and their connectivities. A comprehensive series of bar charts is also included to allow structure types to be assigned to chemical shift data. This handbook is an invaluable resource for all scientists working with phosphorus compounds, including chemists, biochemists, medical researchers, and pharmaceutical chemists.
Download or read book Proton Carbon and Phosphorus Nuclear Magnetic Resonance Studies of Cis poly p phenylene Benzobisoxazole in Polyphosphoric Acid written by Claudia Marlene Ocampo and published by . This book was released on 1995 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multinuclear Solution and Solid State Nuclear Magnetic Resonance Spectroscopic Studies of Selected Organometallic Compounds written by Julian Mark Keates and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Phosphorus 31 and Deuterium Solid state Nuclear Magnetic Resonance Studies of the Headgroup Conformation of Phosphonolipids in Biological and Model Membranes written by Marie-Rose Van Calsteren and published by . This book was released on 1991 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solid-state nuclear magnetic resonance (NMR) techniques were applied to the study of the phase behavior and to the determination of the headgroup conformation of phosphonolipids, both natural and synthetic. The results are compared with those for analogous phospholipids in biological and model membranes. $\sp{31}$P NMR was used to characterize the phase behavior of phospho- and phosphonolipids present in polar and total lipid extracts of the protozoa Tetrahymena thermophila. The $\sp{31}$P NMR spectra of aqueous dispersions of polar and total lipids consist in the partial superposition of two powder patterns, one for each phosphorus-containing lipid class. At low temperature, both lipid extracts give rise to lineshapes characteristic of the lamellar structure. Spectra of the polar lipids show that between 15 and 40$\sp\circ$C, a broad, reversible transition from bilayer to hexagonal phase takes place. On the other hand, the phase behavior for total lipids is different: no hexagonal phase is formed, the lipids remain in the bilayer phase at a higher temperature, and a transition to an isotropic phase occurs between 35 and 40$\sp\circ$C, which is not easily reversible. A large proportion of ethanolamine-containing lipids, both phosphate and phosphonate analogs, is responsible for the hexagonal phase formation observed with the polar lipids. When neutral lipids are present with the polar lipids, the bilayer is stabilized up to a higher temperature. One of the neutral lipid components, tetrahymanol, a pentacyclic triterpenoid, is believed to be responsible for this stabilization. The results show that the conformation of the headgroup up to the phosphorus atom is very similar in phospho- and phosphonolipids, i.e. the C2-C3-O-P torsion angle is nearly trans and the C3-O-P-C1 angle variable over the range of values investigated, with a bend at the phosphorus atom. Contrary to the phosphodiester moiety in analogous phospholipids which adopts a gauche-gauche conformation, two solutions for the next torsion angle O-P-C1-C2 were found around 100 and 130$\sp\circ$. The last segment P-C1-C2-N is nearly trans, whereas the corresponding O-C1-C2-N segment in phospholipids is gauche. Despite the differences in the torsion angle values, the overall appearance of the headgroup is similar for both phospho- and phosphonolipids. The headgroup first extends out of the bilayer plane, bending at the phosphorus atom and the terminal portion lies nearly parallel to the membrane surface. (Abstract shortened by UMI.).
Download or read book Proton Solid state Nuclear Magnetic Resonance Studies of Zeolite Catalysts written by Jeffery Lane White and published by . This book was released on 1992 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Magnetic Resonance Studies of the High Temperature Superconductors in the Normal and Superconducting States written by Nicholas James Curro and published by . This book was released on 1998 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Handbook of Phosphorus 31 Nuclear Magnetic Resonance Data written by John C. Tebby and published by CRC Press. This book was released on 1990-12-26 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: To fully utilize Nuclear Magnetic Resonance (NMR) spectroscopy, a comprehensive and well-organized compilation of NMR data is necessary. While compilations have been available for other important NMR nuclei, such as carbon and fluorine, no comprehensive collection of data has been prepared for phosphorus-until now. The CRC Handbook of Phosphorus-31 Nuclear Magnetic Resonance Data provides a collection of 31P NMR chemical shifts for nearly 20,000 organic and inorganic phosphorus compounds. Each class of phosphorus compound is discussed. Bond types, stereochemistry (with the exception of metal complexes), media, important coupling constants, and data sources are included. The information is systematically organized according to coordination state, the atoms bound to phosphorus, and their connectivities. A comprehensive series of bar charts is also included to allow structure types to be assigned to chemical shift data. This handbook is an invaluable resource for all scientists working with phosphorus compounds, including chemists, biochemists, medical researchers, and pharmaceutical chemists.
Download or read book Nuclear Magnetic Resonance Studies of High Temperature Superconductors written by Krzysztof R. Górny and published by . This book was released on 1999 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metastable Microstructures written by Dipankar Banerjee and published by . This book was released on 1993 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metallic Alloys Experimental and Theoretical Perspectives written by J.S. Faulkner and published by Springer Science & Business Media. This book was released on 1994-02-28 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of new materials is recognized as one of the major elements in the overall technological evolution that must go on in order to sustain and even improve the quality of life for citizens of all nations. There are many components to this development, but one is to achieve a better understanding of the properties of materials using the most sophisticated scientific tools that are available. As condensed matter physicists and materials scientists work toward this goal, they find that it is useful to divide their efforts and focus on specific areas, because certain analytical and theoretical techniques will be more useful for the study of one class of materials than another. One such area is the study of metals and metallic alloys, which are used in the manufacture of products as diverse as automobiles and space stations. Progress in this area has been very rapid in recent years, and the new developments come from many different countries. For these reasons the Advanced Research Workshop Programme in the NATO Scientific Affairs Division has seen fit to sponsor several meetings to bring together the researchers and students working in this field from the NATO countries and elsewhere. There have been a series of NATO-ASI's that have dealt with the results of research on the electronic structure of materials and the properties of metals, alloys, and interfaces. They are: "Electrons in finite and infinite structures" P. Phariseau and L.
