Variable temperature magic-angle

Variable-Temperature Magic-Angle Spinning Carbon-13 NMR Studies of Solid Polymers... 

In this section, initial spectral data on several polymers are reported to illustrate the utility of variable-temperature magic-angle spinning (VT-MAS) for the study of macromolecules in the solid state. 

B. E. Hanson, M. J. Sullivan, R. J. Davis, Direct Evidence for Bridge Terminal Carbonyl Exchange in Solid Dicobalt Octacarbonyl by Variable-Temperature Magic Angle Spinning C-13 NMR-Spectroscopy. J. Am. Chem. Soc. 1984, 106, 251-253. 

Characterization of Molecular Motion in Solid Polymers by Variable Temperature Magic Angle Spinning °C NMR... 

X-ray diffraction shows that at room temperature Fe3(CO)i2 is orientationally disordered about a crystallographic center of symmetry variable-temperature magic-angle-spinning (MAS) C NMR shows that it undergoes a dynamic process (in the solid state), having an estimated activation energy of ca. 10 kcalmoC, which is frozen out at 180 Whether or not these two observations are related... 

The inclusion of a variable temperature magic-angle spinning capability for solid state NMR spectroscopy makes feasible the investigation by relaxation parameters of structural and motional features of polymers above and below Tg and in temperature regions of secondary relaxations. Herein, we report variable temperature (50K to 323K) spectral data on semicrystalline poly(propylene) and glassy PMMA. Illustrative of the data are the Tj and results for isotactic... 

The NMR measurements were performed on a high resolution solid state NMR spectrometer (MSL 300, Bruker). The 29Si spectra were obtained at 60 MHz and recorded at room temperature. Magic-angle sample spinning was routinely carried out at 4 kHz with Kel-f rotors. The CP/MAS spectra were obtained under Hartmann-Hahn conditions (coi = 3 x lO rad s ) in single-contact experiments by using variable contact times from 1 to 50 ms, and a pulse repetition rate of 10 s. All chemical shifts are reported with respect to TMS. 

It has been demonstrated that cross-polarization/magic-angle spinning (CP/MAS) NMR spectroscopy is the most powerful means available to characterize the structure and dynamics of inorganic polymers in the solid state [1], The most recent development of a variable-temperature (VT) spinner provided an indispensable means to study slow chemical exchange, molecular motion and phase transitions of inorganic polymers. 

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