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Updated: Sep 22, 2025

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
Published on: September 26, 2016
Long-Time Diffusion in Polymer Melts Revealed by 1H NMR Relaxometry
R Meier1, A Herrmann1, B Kresse2
1Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany.
Abstract:
We demonstrate that field-cycling 1H NMR relaxometry can be used as a straightforward method of determining translational diffusion coefficient D = D(M) in polymer systems. The 1H spin-lattice relaxation dispersion for polybutadiene of different molecular masses M (446 < M/(g mol-1) < 9470) is measured at several temperatures (233 < T/K < 408) in a broad frequency range. The diffusion coefficient D(T) is determined from the intermolecular contribution to the overall spin-lattice relaxation rate R1(ω), which dominates in the low-frequency range and follows a universal dispersion law linear in √ω. The extracted diffusion coefficients are in good agreement with the values obtained previously by field gradient NMR. The molecular mass dependence D = D(M) exhibits two power laws: D ∝ M-1.3±0.1 and ∝M-2.3±0.1. They show a crossover for M = 2300, a value that is close to the entanglement molecular mass Me of polybutadiene. The corresponding power-law exponents are close to the prediction of the tube-reptation model.
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