Nuclear magnetic resonance broad line

In this review the definition of orientation and orientation functions or orientation averages will be considered in detail. This will be followed by a comprehensive account of the information which can be obtained by three spectroscopic techniques, infra-red and Raman spectroscopy and broad line nuclear magnetic resonance. The use of polarized fluorescence will not be discussed here, but is the subject of a contemporary review article by the author and J. H. Nobbs 1. The present review will be completed by consideration of the information which has been obtained on the development of molecular orientation in polyethylene terephthalate and poly(tetramethylene terephthalate) where there are also clearly defined changes in the conformation of the molecule. In this paper, particular attention will be given to the characterization of biaxially oriented films. Previous reviews of this subject have been given by the author and his colleagues, but have been concerned with discussion of results for uniaxially oriented systems only2,3). 

In some cases, the symmetrical location of the hydrogen atom can be proved, as in KHF2, by broad-line nuclear magnetic resonance studies and by the absence of residual entropy (see below). However, it is not always clear... 

Broad-line nuclear magnetic resonance has been used to study melting in stearic acid and a mesomorphic crystalline to waxy) phase transition in lithium stearate. Extensive motion, liquidlike, though less extensive than that in an isotropic free-flowing liquid, takes place within the system below the melting point of stearic acid or the crystalline to waxy phase transition of lithium stearate. The amount of liquid-like character, as measured by the intensity of a narrow component in the NMR spectrum relative to the total intensity of the whole spectrum, depends on the presence of impurities in the system and even more significantly on whether and how many times the sample has been melted. 

The static methods include determinations of heat capacities (including differential thermal analysis), volume change, and, as a consequence of the Lorentz-Lorenz volume-refractive index relationship, the change in refractive index as a function of temperature. Dynamic methods are represented by techniques such as broad-line nuclear magnetic resonance, mechanical loss, and dielectric-loss measurements. 

Another technique which is of considerable importance in determining orientation in polymers is broad line nuclear magnetic resonance. In a solid polymer at low temperatures when molecular motions are quenched. 

Kashiwagi et al. ° have shown that Wright s data on Perspex are consistent with the predictions of a Ward aggregate model, using orientation functions obtained by broad line nuclear magnetic resonance. 

The numerical value of the glass-transition temperature depends on the rate of measurement (see Section 10.1.2). The techniques are therefore subdivided into static and dynamic measurements. The static methods include determinations of heat capacities (including differential thermal analysis), volume change, and, as a consequence of the Lorentz-Lorenz volume-refractive index relationship, the change in refractive index as a function of temperature. Dynamic methods are represented by techniques such as broad-line nuclear magnetic resonance, mechanical loss, and dielectric-loss measurements. Static and dynamic glass transition temperatures can be interconverted. The probability p of segmental mobility increases as the free volume fraction / Lp increases (see also Section 5.5.1). For /wlf = of necessity, p = 0. For / Lp oo, it follows that p = 1. The functionality is consequently... 

The purpose of this paper is to present some of the results of studies on structure and properties of poly(amino acid) solids. Methods employed in this work include X-ray diffraction, broad-line nuclear magnetic resonance, electron spin resonance, dynamic mechanical, and dielectric methods. Poly(amino acid)s studied here are mostly poly(glutamate)s which include poly(y-benzyl L-glutamate), poly(y-methyl L-glutamate), and others. 

The most early investigation of molecular motions occurring in poly(amino acid) in the solid state was made by means of broad-line nuclear magnetic resonance(NMR) by Kail et al. [18]. They showed that side chains of poly(amino acid) undergo considerable motions in the solid state. Since then, several workers have made NMR measurements on a variety of poly(aiiiino acid)s[19-21]. ... 

McBrierty, V.J. and Ward, I.M. (1968) Investigation of the orientation distribution functions in drawn polyethylene by broad line nuclear magnetic resonance. J Phys D Appl. Phys., 1, 1529. 

Local mode relaxation of isolated lignin and its model compounds have been detected by dynamic mechanical measurement, and broad-line nuclear magnetic resonance spectroscopy (b-NMR) [49,53], although this molecular motion has scarcely received attention in recent papers. Transition map of local mode relaxation of various kinds of polymers is found elsewhere [56]. Figure shows second moment of absorption line of b-NMR of DL in powder form. When the relaxation is from the... 

Solid state materials have been studied by nuclear magnetic resonance methods over 30 years. In 1953 Wilson and Pake ) carried out a line shape analysis of a partially crystalline polymer. They noted a spectrum consisting of superimposed broad and narrow lines which they ascribed to rigid crystalline and amorphous material respectively. More recently several books and large articles have reviewed the tremendous developments in this field, particularly including those of McBrierty and Douglas 2) and the Faraday Symposium (1978)3) —on which this introduction is largely based. 

Since about 1960 nuclear magnetic resonance (NMR) spectroscopy has become an important tool for the study of chain configuration, sequence distribution and microstructure of polymers. Its use started from early broad-line studies of the one-set of molecular motion in solid polymers and passed through the solution studies of proton NMR, to the application of the more difficult but more powerful carbon-13 NMR methods to both liquids and solids. 

Nuclear magnetic resonance (NMR) spectroscopy has proved to be a method of considerable interest and importance for the study of polymers, and during the past 10—12 years a large number of investigations of a variety of polymer systems have been published. This work has been ably reviewed by Slighter (7). These studies have dealt with solid polymers and the spectra obtained have been of the so-called broad-band or "wide-line type. In such polymer spectra, as in the... 

FIGURE 8.7 31P NMR spectra of Na2HP03 (202 MHz, 11.7 T) at the temperatures indicated. At 225 K, where >0Tt < 1, the low frequency line is so broad that it is unobservable. From Farrar and Stringfellow,94 Encyclopedia of Nuclear Magnetic Resonance, D. M. Grant and R. K. Harris, Eds. Copyright 1996 John Wiley Sons Limited. Reproduced with permission. 

Nuclear magnetic resonance (NMR) spectroscopy is at present one of the most widely applied physical techniques in biology, and its potential applications increase day by day, as more sophisticated instrumentation becomes available and deeper theoretical knowledge is obtained. The phenomenon of NMR was discovered simultaneously by Purcell and his associates at Harvard University and by Bloch and co-workers at Stanford University, for which they were jointly awarded the Nobel prize in physics in 1952. In the lipid field there are two main types of NMR spectroscopy that are of interest broad-line experiments, concerned mainly with the spectra obtained from samples in the solid state, or from oriented phases, and narrow-line, or high-resolution, experiments carried out with samples in the liquid, solution or gas phases. Both types of NMR spectroscopy are extremely useful in the study of the lipids. In addition, Fourier transform (FT) NMR has helped increase the sensitivity of the technique and the so-called pulse method of recording spectra has literally widened the prospect of NMR applications in the field of lipid research and industry. The application of NMR to solid fats is still in its infancy (Pines et aL, 1973 Schaefer and Stejskal, 1979 BocieketaL, 1985). 

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