Long-Time Diffusion in Polymer Melts Revealed by 1H NMR Relaxometry

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• 作者：R. Meier ; A. Herrmann ; B. Kresse ; A. F. Privalov ; D. Kruk ; F. Fujara ; E. A. R枚ssler
• 刊名：ACS Macro Letters
• 出版年：2013
• 出版时间：February 19, 2013
• 年：2013
• 卷：2
• 期：2
• 页码：96-99
• 全文大小：271K
• 年卷期：v.2,no.2(February 19, 2013)
• ISSN：2161-1653

文摘

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鈥搇attice relaxation dispersion for polybutadiene of different molecular masses M (446 < M/(g mol^鈥?) < 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鈥搇attice relaxation rate R₁(蠅), which dominates in the low-frequency range and follows a universal dispersion law linear in 鈭毾? 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^鈥?.3卤0.1 and M^鈥?.3卤0.1. They show a crossover for M = 2300, a value that is close to the entanglement molecular mass M_e of polybutadiene. The corresponding power-law exponents are close to the prediction of the tube-reptation model.