The effect of crosslinking in elastomers investigated by NMR analysis of C-13 edited transverse H-1 NMR relaxation

The transverse nuclear H-1 magnetization decay in poly(styrene-co-butadiene) (SBR) is investigated by editing C-13 NMR spectra. This technique allows for the assignment of localized H-1 dynamical information by discriminating the chemical sites based on their chemical shift in the C-13 dimension. Here, the home- and heteronuclear dipolar couplings contribute to the H-1 NMR relaxation giving additional information to a homonuclear experiment. In this heteronuclear 2D experiment two prominent peaks are observed in the C-13 dimension, which correspond to CH and CH2 groups, respectively. The decay rate in the H-1 dimension is found for both groups to scale with the crosslink density. An additional ultra-fast magnetization decay is reported. The effect of the carbon black filler is investigated for this component. The analysis of the C-13 NMR edited transverse H-1 magnetization relaxation is a useful tool in combining high resolution NMR spectra with information on molecular dynamics, providing insight into crosslink density and filler effects.