Abstract:

The 1H MAS spectrum of a plastic organic solid is usually composed of a high-resolution component and a broadline component. The high-resolution component corresponds to a plastic phase, while the broadline component corresponds to the rigid Phase. The high-resolution spectrum of the plastic phase can be observed by the echo-MAS experiment with a long echo time; the high-resolution spectrum of the whole 1H system can be observed by the CRAMPS technique, mainly coming from the contribution of the rigid phase at usual temperature. It is shown that combination of CRAMPS with 1H MAS and echo-MAS is an effective way for studying the ratio of the plastic phase to the rigid phase, molecular structure and states of motion in organic solids.

Key words: Solid-state ¹H NMR, Plastic organic solid, MAS, Echo-MAS, CRAMPS