Linear poly(propylene glycol) (PPG) as well as a poly(propyleneimine) (PPI) dendrimer with different molar masses (M) are investigated by field-cycling (FC) 1 H NMR, shear rheology (G) and dielectric spectroscopy (DS). The results are compared in a reduced spectral density representation: the quantity R 1 (ωτ α )/R 1 α (0), where R 1 (ωτ α ) is the master curve of the frequency dependent spin−lattice relaxation rate with τ α denoting the local correlation time, is compared to the rescaled dynamic viscosity η′(ωτ α )/η′ α (0). The quantities R 1 α (0) and η′ α (0), respectively, are the zerofrequency limits of a simple liquid reference system. Analogously, the dielectric loss data can be included in the methodological comparison. This representation allows quantifying the sensitivity of each method with respect to the polymer-specific relaxation contribution. Introducing a "cumulative mode ratio" F i (M) for each technique i, which measures the zero-frequency plateau of the rescaled spectral density, characteristic power-law behavior F i (M) ∝ M α i is revealed. In the case of PPG, F NMR (M), F G (M), and F DS (M) essentially agree with predictions of the Rouse model yielding characteristic exponents α i . The crossover to entanglement dynamics is identified by a change in α i around M ≅ 10 kg/mol. The analysis is extended to the dendrimer which exhibits a relaxation behavior reminiscent of Rouse dynamics. Yet, clear evidence of entanglement is missing. The M-dependencies of the dendrimer diffusion coefficient D obtained by pulsed field-gradient NMR and the zero-shear viscosity are found to be D(M) ∝ M −1.6±0.2 and η(M) ∝ M 1.9±0.2 , respectively, in good agreement with our theoretical prediction η(M) ∝ M 1/3 D −1 (M). The close correspondence of R 1 (ωτ α ) with η′(ωτ α ) establishes FC NMR as a powerful tool of "molecular rheology" accessing the microscopic processes underlying macroscopic rheological behavior of complex fluids.

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