Mixtures of protonated and deuterated polybutadiene and polydimethylsiloxane are studied by means of field-cycling (FC) H-1 NMR relaxometry in order to analyze the intra- and intermolecular contributions to spin-lattice relaxation. They reflect reorientational and translational dynamics, respectively. Master curves in the susceptibility representation chi ''(omega tau(s)) are constructed by employing frequency-temperature superposition with tau(s) denoting the segmental correlation time. The intermolecular contribution is dominating at low frequencies and allows extracting the segmental mean square displacement < R-2(t)>, which reveals two power-law regimes. The one at short times agrees with t(0.5) predicted for the free Rouse regime and at long times a lower exponent is observed in fair agreement with t(0.25) expected for the constrained Rouse regime of the tube-reptation model. Concomitantly the reorientational rank-two correlation function C-2(t/tau(s)) is obtained from the intramolecular part. Again two power-law regimes t(-epsilon) are identified for polybutadiene. The first agrees with t(-1) of free Rouse dynamics whereas at long times epsilon = 0.49 is obtained. The latter is corroborated by the H-2 relaxation of deuterated polybutadiene, yet, it does not agree with epsilon = 0.25 predicted for constrained Rouse dynamics. Thus, the relation C-2(t) alpha < R-2(t)>(-1) as assumed by the tube-reptation model is not confirmed.