Cross-polarization-magic angle spinning CP/MAS technique

The dehydrohalogenation products of poly(ethylene-a/z-chlorotrifluor-oethylene) were also studied using solid-state NMR spectroscopy and the cross-polarization magic angle spinning (CP MAS) technique [18]. The elimination reaction induced by potassium ZerZ-butoxide (z-BuOK) in tetrahydrofuran (THF) was found to proceed slowly only 50% of hydrogen... 

Charge Densities - CP/MAS NMR Spectroscopy. Recent C NMR studies of solid carbohydrates using the cross-polarization/magic angle spinning (CP/MAS) technique (15) demonstrates that NMR chemical shifts of the Cl, C4 and C6 carbon atoms are considerably displaced, up to 1C ppm, depending on the particular structure. A relation of these shifts to conformation would be valuable in learning whether a conformation is retained in non-crystalline or solution states. 

This is the most promising nondegradative technique for humic structural analysis. This is primarily due to two fundamental instrumental advances the Fourier transform technique and the cross-polarization/ magic-angle spinning (CP/MAS) technique which allows the acquisition of NMR spectra from solid samples. The H and NMR spectra of all humic substances are highly resolved and exhibit several peaks. 

Until recently, insolubility prevented the use of NMR spectroscopy as a routine tool for PPP characterization. In 1980, the first solid-state NMR spectrum ( C) of PPP was obtained by use of cross-polarization magic-angle spinning (CP/MAS) techniques [201]. Since that time other C NMR and H NMR studies have been reported [202,203]. Furthermore, the development of the metal-catalyzed route to substituted PPPs has made it possible to use this technique routinely, for structural characterization in solution [73-82]. 

In this section, we will concern ourselves mainly with relaxation processes in solid polymer samples, as distinct from high-resolution NMR used for diagnosing the chemical structure of molecules. The latter can be done on solid samples using cross-polarization, magic-angle spinning (CP-MAS), but these techniques can eliminate valuable information on the very relaxation processes of interest to us. An interesting exception, however, is the WISE experiment, which is discussed below. 

Cellulose, which Is one of the most abundant organic substances found In nature, has been extensively studied by various techniques such as x-ray scattering, electron microscopy, IR and Raman spectroscopy, NMR spectroscopy etc. However, the crystal structure and noncrystalline state are not yet solved for cotton, ramie, bacterial and valonla celluloses which can be easily obtained in pure form. Cross-polarization/magic angle spinning(CP/MAS) C NMR spectroscopy is a promising new method to study these unsolved problems of cellulose, because this method is very sensitive to local molecular conformations and dynamics. 

The Si NMR [19] cross-polarization magic-angle spinning (CP MAS) and H NMR magic-angle spinning with multiple-pulsed line narrowing (CRAMPS for combined rotation and multiple-pulse spectroscopy) techniques of Maciel et al. [20,21] indicate that FS-662... 

The primary components and the chemical structure of the raw peat and the solid product were further analyzed by Fourier transform infrared spectroscopy (FTIR) 0ASCO 670 Plus) using the Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) technique and the JASCO IR Mentor Pro 6.5 software for spectral analysis. The cross polarization/magic angle spinning (CP/MAS) NMR spectrum of raw peat and the solid... 

Among the more recent contributions to this field, some [32-35] call upon the use of new characterization techniques, like diffuse reflectance infra red fourier transform (DRIFT) and cross polarized magic angle spinning (CP-MAS) C-NMR spectroscopy. 

In recent years new NMR techniques offering broad applications in stereochemical analysis have come into use. A prominent example is 2D-NMR (both 2D-resolved and 2D-correlated spectroscopy), which has been extensively applied to biopolymers (149-151). Its use with synthetic polymers has, until now, been limited to but a few cases (152, 153). A further technique, cross-polarization magic-angle spinning spectroscopy (CP-MAS NMR) will be discussed in the section on conformational analysis of solid polymers. 

Cook, R., and Langford, C. (1999). Ramped amphtude cross polarization magic angle spinning NMR (Ramp-CP-MAS-NMR) A technique for quantitative study of the composition of solid state polymers. Polymer News 24, 6-15. 

The direct determination of the aromaticity in coal was first reported by VanderHardt and Retcofsky (9) using nonspinning carbon-13 NMR techniques. More refined studies using a combination of cross-polarization and magic-angle spinning (CP/MAS) has been used to examine the aromaticity in a number of different coals (10, ll). 

---