High resolution nuclear magnetic resonance techniques

Abstract This chapter describes the experimentai compiement of theoretical models of the microscopic mechanism of ferroelectric transitions. We use the hydrogen-bonded compounds as examples, and attempt to show that the new experimental data obtained via recently developed high resolution nuclear magnetic resonance techniques for solids clearly support the hypothesis that the transition mechanism must involve lattice polarizability (i.e. a displacive component), in addition to the order/disorder behaviour of the lattices. 

The advanced scattering methods,such as high resolution nuclear magnetic resonance techniques (HR-NMR), the NMR-spin diffusion, non-radiative energy transfer, excimer fluorescence, thermally stimulated depolarization current, small angle neutron scattering, SANS and FT-IR, are more appropriate for the task. For example, the NMR spin-lattice relaxation times, Tj, distinguishes > 2 nm and it may be used for either molten or solidified specimens " ... 

Chemical constitution, steric configuration and, in some cases, details about chain conformation, aggregation, association, and supramolecular self-organization behavior of macromolecular substances can be determined using high-resolution nuclear magnetic resonance (NMR) spectroscopy. This spectroscopic technique is sensitive towards nuclei with a nuclear spin different from zero. 

This article will review the impact of two powerful new techniques for characterizing epoxy resins at the molecular level — Fourier transform infrared spectroscopy (FT-IR) and high resolution nuclear magnetic resonance (NMR) of solids. Fortunately, these two techniques are not inhibited appreciably by the insoluble nature of the cured resin. Consequently, substantial structural information at the molecular level can be obtained. In this article, the basis of the methods will be briefly described in order to appreciate the nature of the methods followed by a description of the work on epoxies to date and finally some indication will be given of the anticipated contributions of these methods in the future. 

Fig. 3.73 Decoupled spectrum of crotonaldehyde. Data reproduced from W. McFarlane and R. F. M. White (1972). Techniques of High Resolution Nuclear Magnetic Resonance Spectroscopy. London Butterworths, p. 28.

High-resolution nuclear magnetic resonance (NMR) spectroscopy is a relatively rapid technique and is highly robust in terms of reproducibility of results. The ubiquity of protons in cellular metabolites and the fact that other nuclei are observable by NMR (e.g., and mean that a relatively large number of different metabolites can be detected. Furthermore, the technique requires minimal sample preparation, and its nondestructive nature allows for more analyses to be... 

W. A. Anderson, "Application of modulation techniques to high resolution nuclear magnetic resonance spectrometers," Rev. Sci. Instrum. 33, 1160-1166 (1962). 

The application of high resolution nuclear magnetic resonance spectroscopy to the study of polymer structure is a field which is now about ten years old and has recently grown very rapidly. This technique is employed in nearly every center of polymer research throughout the world and can claim a place as a major tool of macromolecular science. The literature alone can attest to this fact. In preparing recent reviews, I found it necessary to refer to nearly 600 substantial papers, and there are many additional ones of more marginal interest. 

Among the techniques more frequently used for elucidating cluster structures are crystallographic studies by both single-crystal X-ray and neutron-diffraction techniques, multinuclear high resolution nuclear magnetic resonance (NMR), and infrared spectroscopy. 

High resolution nuclear magnetic resonance is the most effective structural technique for studies in solution. Although in some ideal cases, such studies can define structure and stereochemistry, it is not possible to obtain structural parameters by this method. Nuclear magnetic resonance techniques have proved to be an excellent method for studying dynamic processes in clusters. 

A large amount of head to head connections was found in some polymers such as poly (vinylidene fluoride) [-CH CF -] and poly (vinyl fluoride) [-CH CHF-] by using the high-resolution nuclear magnetic resonance spectroscopy technique. 

The determination of the secondary and tertiary structure—that is, the details of the three-dimensional folding of the polypeptide chain of a protein at high resolution—relies on one of two powerful techniques x-ray diffraction analysis of protein crystals and multidimensional high-field nuclear magnetic resonance (NMR) spectroscopy. Both methods provide very detailed structural in-... 

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