Spin interactions, intersegment

Equations 63 and 64 are valid for intrasegment spin interactions. Since the Rouse model is experimentally relevant mainly for modes of relatively short chains or short chain sections, any contribution from intersegment dipolar interactions are neghgible on this time/frequency scale, and need not be treated expHcitly. 

Intra- and Intersegment Spin Interactions (Dispersion Region iii)... 

That is, dispersion region III is explained by the dominance of this intersegment contribution, whereas regions I and II are dominated by intrasegment spin interactions. 

Apart from these two relaxation dispersion regimes, which are mainly based on intrasegment spin interactions (and possibly nearest neighbor intersegment contributions), a third dispersion region specific for dipolar-coupled nuclei exists at low frequencies. This was shown to be due to (longdistance) dipolar interactions being relevant for protons but not for deuter-... 

Fig. 29. Proton spin-lattice relaxation time of polyethyleneoxide (PEO) melts as a function of the frequency [49]. The data refer to the molecular weight independent chainmode regime II (low-mode-number limit) and regime III influenced by intersegment dipolar interactions [154]...

Fig. 30a, b. Proton spin-lattice relaxation times in the laboratory system (Ti) and in the rotating frame (Tip) of polyisoprene (PIP) melts as a function of the frequency (v, Lar-mor frequency in the laboratory frame Vi=yBi/(2 r), rotating-frame nutation frequency) [125]. The data refer to the molecular weight independent chain-mode regime II (low-mode-number limit) and regime III influenced by intersegment dipolar interactions [154]. a Comparison of Tj and Tip data. The arrow is to indicate the crossover frequency between regions I and II. hhp data in detail... 

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