The influence of polymer molecular-weight distributions on pulsed field gradient nuclear magnetic resonance self-diffusion experiments |
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Authors: | B Håkansson M Nydén O Söderman |
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Institution: | (1) Division of Physical Chemistry 1 Center for Chemistry and Chemical Engineering, Lund University P.O. Box 124, S-221 00 Lund, Sweden, SE;(2) Department of Applied Surface Chemistry Chalmers University of Technology S-412 96 Gothenburg, Sweden, SE |
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Abstract: | The influence of polymer molecular-weight distributions on the outcome of pulsed field gradient (PFG) NMR self-diffusion
experiments has been considered. The self-diffusion coefficient, D, of monodisperse poly(ethylene oxide) (PEO) polymers has been determined in order to accurately determine the scaling behavior
of D both with molecular weight and concentration. In order to investigate the influence of polydispersity on the PFG NMR signal,
a model system consisting of ten reasonably monodisperse PEO polymers was made, and the PFG NMR signal intensities were recorded
at a low total concentration. The data were analyzed using both inverse Laplace transformation and nonlinear least-squares
fitting to a prescribed distribution function of D. Finally, the molecular-weight distribution was obtained by use of the values of the scaling parameters. We also present
some model calculations used to investigate the sensitivity of the degree of polydispersity on the NMR signal decays.
Received: 27 May 1999 Accepted in revised form: 19 October 1999 |
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Keywords: | Polymers Poly(ethylene oxide) Pulsed field gradient spin-echo nuclear magnetic resonance Self-diffusion Polydispersity |
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