MOLECULAR-DYNAMICS IN SIDE-GROUP POLYMERS WITH AND WITHOUT LIQUID-CRYSTALLINE PHASES FROM H-2 NMR

Side-group liquid crystalline polymers were investigated by 1 D and 2 D solid state H-2 NMR methods in the glassy state. The side-group dyna mics of liquid crystalline systems were compared to those of amorphous systems of the same molecular architecture. The onset of fast rotatio nal motion of the phenylene rings additionally to phenylene flips was detected at considerably lower absolute and reduced temperature in the liquid crystalline systems indicating the influence of the ordered st ate on local dynamics. In 2D exchange spectra, the lineshapes are part icularly sensitive towards possible slow motion of the flip axis itsel f which could be envisaged to fluctuate within the orientational distr ibution of the mesogen. However, the experimental spectra for the inve stigated side-group liquid crystalline polymers show no indication of the characteristic features, thereby proving that the flip axis is rig id within +/- 3-degrees even after a large number of flips.