DETERMINING ORDER IN POLYMERS VIA MULTIDIMENSIONAL SLOW-MAGIC-ANGLE-SPINNING DECODER NMR

Two multidimensional solid-state NMR experiments for quantifying order in oriented systems such as extruded polymers are presented. The firs t experiment correlates the C-13 anisotropic chemical shift at two dif ferent orientations with respect to the external magnetic field using a slow rotation about the magic angle for sample reorientation and rep resents a new version of the DECODER experiment. The second experiment separates the two-dimensional anisotropic chemical-shift patterns wit h respect to their isotropic chemical shifts in a third dimension. Thi s alleviates the need to analyze multiple overlapping resonances and a llows the determination of orientation distributions of individual sit es. The incorporation of ultraslow MAS to reorient the sample consider ably reduces the instrumental requirements of the DECODER experiment. (C) 1995 Academic Press, Inc.