THE ORIENTATION DISTRIBUTION IN AN INDUSTRIAL-SAMPLE OF POLY(P-PHENYLENETEREPHTHALAMIDE) DETERMINED BY 2-DIMENSIONAL AND 3-DIMENSIONAL NMR TECHNIQUES

Two new solid-state NMR methods for measuring orientation distribution s in partially ordered solids are applied to high tensile-strength fib re polymers. Both methods use the anisotropy of the carbon-13 chemical shift tensor as a probe for local molecular directions, but they diff er in the manner in which the information is extracted and complement one other. The spectral resolution is higher in the ORDER (ORientation Distributions with Enhanced Resolution) experiment, which employs rot or-synchronized three-dimensional magic angle spinning (MAS) NMR, whil e the angular precision with which the orientation distribution can be determined is higher in the DECODER (Direction Exchange with Correlat ion of Orientation Distribution Evaluation and Reconstruction) experim ent. The utility of the two techniques is demonstrated by their applic ation to the study of industrially produced poly(p-phenyleneterephthal amide) fibres. Both give the same result for the width (($) over bar c hi = 13 degrees) and the order parameters (<P-2> = 0.85, <P-4> = 0.57, <P-6> = 0.34, <P-8> = 0.14) Of the orientation distribution.