SEGMENTAL DYNAMICS IN THE AMORPHOUS PHASE OF NYLON-66 - SOLID-STATE H-2 NMR

Solid-state deuterium NMR spectroscopy coupled with line shape simulations has been used to examine the segmental dynamics of individual methylene sites and N-D sites within the amorphous domains of selectively deuterated nylon 66 polymers over a wide temperature range. Magnetization only from amorphous domains may be isolated via spin-lattice relaxation time discrimination due to the presence of small-angle fluctuations (librations) at all sites within the amorphous domains above -50 °C. The N-D sites exhibit very little motion below Tg, and above Tg a fraction of the sites undergo nearly isotropic motion. The C-D sites exist in two discrete environments below Tg (not a continuous distribution): one of the populations exhibits only librational motion and the other exhibits both librational and internal rotation (γ-relaxation) motions. Above Tg, a fraction of the C-D sites undergo nearly isotropic motion (essentially the same fraction as the N-D sites), and this behavior of the entire repeat unit is identified with the a relaxation. The addition of 2 ± 0.3 wt % water has no apparent effect upon the γ relaxation and depresses the α process by approximately 40 °C; additionally, T2 relaxation data indicate that the β relaxation is a process which involves all C-D sites and is observed only in wet polymer. © 1990, American Chemical Society. All rights reserved.