HOMONUCLEAR SEPARATED LOCAL-FIELD SPECTROSCOPY BY MAGNETIZATION-EXCHANGE NMR

The possibility to perform homonuclear separated-local field NMR spect roscopy by magnetization-exchange is presented. Solid-state one-dimens ional proton magnetization-exchange NMR is used to investigate intergr oup residual dipolar couplings in cis-1,4-polybutadiene elastomer. A t hree-spin model is employed, in which the CR-and CH2-protons are consi dered to be coupled by residual dipolar interactions. The magnetizatio n-exchange process between the CH- and the CH2-group in the regime of short mixing time provides valuable insight regarding molecular order. The spin-system response reflects well-localized dipolar interactions . The residual intergroup dipolar couplings are measured along the ave rage polymer-chain direction for different temperatures. The dynamic o rder parameter along the chains is also evaluated.