New measurements of chain self-diffusion (D) in highly entangled hydrogenated polybutadiene solutions and melts indicate that D ∼ M-2.3 ± 0.1, where M is the molecular weight. Although these results contradict the widespread belief that in melts D ∼ M-2.0, we demonstrate that in fact the literature data for seven different polymers are consistent with D ∼ M-2.28±0.05. This result largely removes a recalcitrant discrepancy between the M exponents for D and the viscosity. Important implications for theoretical approaches are also noted. 1999
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