The other mode (Dmed,1), represented in Figure is obtained as a fitting result to the data points of the build-up curve after those that correspond to the highly cross-linked regions (step-up), and thus represent the bulk of the sample. In SBR, prolonged exposure leads to further stiffening with a net Dmed,1 gain of about 33%. Likewise, σln,1 shows an increase in the coupling distribution due to chain modifications.