Visualization of residual anisotropic interactions in crosslinked natural rubbers by dipolar local field measurements and H natural abundance NMR spectroscopy

An extension of the exploitation of indirect observation of ¹H nuclei through ¹³C resonances is presented in the case of crosslinked elastomers. It is demonstrated that, by using this method in vulcanized elastomers above T_g a direct visualization of residual dipolar interactions on different functional groups as well as their dependence on motional constraints is available. It is also shown that ²H natural abundance NMR spectra of elastomers provide similar information on motional constraints by way of residual quadrupolar interactions.