With SBR, weathering to 988 h shows a reversal of cross-linking trend. The average coupling strength reduced from 0.377 kHz (after 504 h) by about 50 Hz to 0.326 kHz (after 988 h). This is a rather surprising finding that was not observed in the low-field experiment. Variations can be observed at resonances ii, iii, and vii (see Figure ), which correspond to the main chain protons of the three monomers in SBR, suggesting changes in the bonding situation in their vicinity due to weathering. But the cross-link distribution remains almost unaffected by weathering.