High-temperature pulsed-field-gradient multidimensional NMR of polymers

The application of pulsed-held-gradient (PFG) techniques has been particula rly important in providing the ability to detect 2D and 3D NMR cross peaks from minor structural components in synthetic organic polymers, The lack of mobility in a large percentage of polymers leads to rapid T-2 relaxation w hich prevents the use of pulse sequences, such as the HMBC experiment, that operate based on coherence transfer via small, long-range J couplings. Hig h-temperature NMR increases molecular motion with corresponding line narrow ing (e.g., polyethylenes are typically analyzed at 120 degrees C). However, until now, the requirement for high temperature has precluded the use of P FG methods. Here we present data from a new probe which is capable of perfo rming high-temperature PFG coherence selection experiments at temperatures typical of those used in many polymer analyses. We illustrate the performan ce of this probe with PFG-HMBC spectra of a copolymer from ethylene/1-hexen e/1-butene at 120 degrees C, (C) 1999 Academic Press.