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

The transverse nuclear ¹H magnetization decay in poly(styrene-co-butadiene) (SBR) is investigated by editing ¹³C NMR spectra. This technique allows for the assignment of localized ¹H dynamical information by discriminating the chemical sites based on their chemical shift in the ¹³C dimension. Here, the homo- and heteronuclear dipolar couplings contribute to the ¹H NMR relaxation giving additional information to a homonuclear experiment. In this heteronuclear 2D experiment two prominent peaks are observed in the ¹³C dimension, which correspond to CH and CH₂ groups, respectively. The decay rate in the ¹H 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 ¹³C NMR edited transverse ¹H 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.