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Cross polarization-magic angle sample spinning NMR studies

With respect to the rotational isomeric states of saturated chain molecules
  • Martin Möller
Conference paper
Part of the Advances in Polymer Science book series (POLYMER, volume 66)

Abstract

At the example of some selected chain molecules temperature dependent Magic Angle Spinning — Cross Polarization NMR is described as an analytical tool for the investigation of solid state conformations and conformational interconversions. High resolution solid state 13C and 29Si spectra of four cyclic molecules, cyclododecane, cyclotetraeicosane, cyclohexatria contane and octamethyltetrasiloxane, are discussed with regard to their thermal behaviour. At the case of poly(1,2-dimethyltetramethylene) CP-MAS NMR spectra of crystalline and glassy materials are compared. As long as no specific interactions have to be considered and the conformations can be described in terms of rotational isomeric states comparable shift variations can be detected for the dissolved, the glassy, and the crystalline state. For the smaller ring molecules a solid state phase of high internal mobility can be seen and correlated with a phase transition detectable by means of DSC. By comparison with X-ray diffraction data the well resolved resonance signals for the low temperature phase were assigned to rotational isomeric states of the carbon-carbon bonds. Chemical shift variations are compared to those due to molecular packing effects. The latter are considerably smaller compared to the conformational effects which are as large as 12 ppm. Significant differences of the conformational characteristics can be reported for cyclododecane in comparison to octamethyltetrasiloxane. It appears that for cyclododecane the solid state phase transition is due to the temperature dependence of the conformational interconversion with respect to the intramolecular barriers of bond rotation. For octamethyltetrasiloxane the solid state phase transition is characterized by a change of the molecular packing which is the reason for the altered rate of conformational interconversion.

Keywords

Cross Polarization Shift Variation Solid State Spectrum Solid State Phase Transition Crystal Conformation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • Martin Möller
    • 1
  1. 1.Institut für Makromolekulare Chemie der Universität Freiburg, Hermann-Staudinger-HausFreiburgGermany

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