THE EFFECT OF CROSS-LINKING 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-buta diene) (SBR) is investigated by editing C-13 NMR spectra. This techniq ue allows for the assignment of localized H-1 dynamical information by discriminating the chemical sites based on their chemical shift in th e 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 prom inent 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 addition al ultra-fast magnetization decay is reported. The effect of the carbo n black filler is investigated for this component. The analysis of the C-13 NMR edited transverse H-1 magnetization relaxation is a useful t ool in combining high resolution NMR spectra with information on molec ular dynamics, providing insight into crosslink density and filler eff ects.