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Improved NMR characterization of high‐molecular‐weight polymers and polyelectrolytes through the use of preliminary ultrasonic degradation by Kulicke, Werner-Michael ;Otto, Matthias ;Baar, Andreas is a Chemistry article available to read on EtoBox.

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## Abstract High‐molecular‐weight polymers, especially ionic polymers, give rise to highly viscous solutions which are likely to entrap air bubbles, even at low concentrations. The ^13^C NMR spectra of these solutions exhibit poor signal‐to‐noise ratios and broad bands due to the shortened __T__~2~ relaxation times. Qualitative evaluation is thus made very difficult, and quantitative evaluation becomes impossible. In ^1^H spectroscopic analysis of xanthan, these problems occur at concentrations as low as 0,5 wt.‐%. A method of viscosity reduction is required that reduces the molecular weight but does not affect the tacticity or comonomer distribution nor lead to the formation of monomers. From the various methods that were examined, ultrasonic degradation was found to be the best means of fulfilling these requirements. This study includes both coiled synthetic polymers, such as polyacrylamide or poly(acrylamide‐__co__‐sodium acrylate), and semirigid biopolymers, such as xanthan or schizophyllan, with a view to finding a generally applicable method. It was shown that the recording time could easily be reduced by a factor of up to 20 and that the resolution was enhanced. No change in

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Author

Kulicke, Werner-Michael ;Otto, Matthias ;Baar, Andreas

Publisher

Wiley (John Wiley & Sons); Wiley (ISSN 0025-116X)

Published

1993

Language

EN

Field

Chemistry (Physical Sciences)