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Polymer additives mixture analysis using pulsed-field gradient NMR spectroscopy

✍ Scribed by Dimuthu A. Jayawickrama; Cynthia K. Larive; Elizabeth F. McCord; D. Christopher Roe

Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
216 KB
Volume
36
Category
Article
ISSN
0749-1581

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✦ Synopsis

The analysis of mixtures is a problem commonly faced in analytical chemistry. In this work, pulsed-Ðeld gradient NMR (PFG-NMR) experiments were used to analyze mixtures of polymer additives and simple polymer solutions. PFG-NMR experiments were also utilized to determine di †usion coefficients of the individual components of a mixture and in this way facilitate resonance assignments. This strategy is particularly useful for molecules containing isolated protons that are not amenable to the standard two-dimensional NMR experiments based on J-coupling. PFG-NMR was also used to edit the NMR spectra of polymer solutions by eliminating the resonances of fast-di †using components such as low molecular weight additives or residual solvent. Di †usion ordered spectroscopy (DOSY) was used for the analysis of the PFG-NMR data. The DOSY method produces a two-dimensional spectrum that correlates chemical shift with the calculated di †usion coefficient, and simpliÐes the analysis of many complex mixtures. For well resolved resonances, the correct di †usion coefficient is unambiguously determined. The DOSY analysis was able to resolve the di †usion coefficients of most of the components in the mixtures examined. However, in some cases of overlapped resonances and components with similar di †usion coefficients, a single di †usion coefficient was determined which was the weighted average of the two components.

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