Solid State CARBON-13 NMR Studies of the Morphology and Orientational Order of Polymer Fibers

A fundamental understanding of the mechanism of fiber formation requires a detailed knowledge of fiber morphology. However due to the limitation of current techniques, the crystallization behavior is still not fully understood. Modern solid state NMR techniques enable one to approach this subject from different aspects. In this work we conducted detailed studies of the morphology of as-spun PET (poly (ethylene terephthalate)) and gel-spun PE (poly (ethylene)) fibers by ^{13}C CP/MAS (Cross Polarization/Magic Angle Spinning) NMR technique. The presence of multiple-component resonance lineshapes allows one to calculate the true population of various morphological components, after correcting for pin relaxation effects. From these NMR measurements, two different models for PET and PE polymer systems have been proposed. We have also employed and further developed the advanced two-dimensional rotor synchronized MAS (2D ROSMAS) technique to study the orientational order of various morphological components. A wide range of orientational order is clearly displayed on 2D spectra for samples under different fabrication conditions. A regression simulation program has been used to deduce the order parameter used in computing the orientational distribution function (ODF) for each component. Our results for the first time provide unique information about orientational order and morphology at the molecular level, thereby providing a much more complete basis for theoretical modeling of polymer system.