Previous assignment of the signals in the spectra of carboxymethylcellulose, based on an incremental calculation and hence on low-molar-mass model substances, made determination of the partial degree of substitution fundamentally impossible because overlapping of the relevant signals was predicted. However, the methods of acid and enzymatic hydrolysis employed generate the monomer or a mixture of polymers, oligomers and monomers and hence a large number of end groups, which also influence the nuclear magnetic resonance (NMR) spectra. By using ultrasound, it was possible to degrade the molar mass (lower limit of molar mass approx. 100000 g/mol), without oligomers being generated and cleavage of side groups occurring. The viscosity of 10 wt.-Vo polymer solutions was so low that the partial degree of substitution could be determined quantitatively for the first time. An additional I3C NMR spectroscopic examination of the acid hydrolysate enabled the composition of the eight monomers of sodium carboxymethylcellulose (NaCMC) to be determined in a degree of substitution (DS) range of 0,8-3,0. Knowledge of the monomer compositions is then used to reassign the signals of the polymer spectra, which are then evaluated. Comparison with titrimetric methods (polyelectrolyte titration and ASTM method) showed some wide discrepancies with the absolute method (NMR) in the case of samples with a DS greater than 1. The results of the 13C NMR spectroscopic examination of the acid hydrolysate were also used to determine the relative rate constants of the etherification reaction ( k , : k , : k , = 3,O : 1,O: 2,1), and these were then compared with published data.

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 13C NMR spectra of these solutions exhibit poor signal-to-noise ratios and broad bands due to the shortened T2 relaxation times. Qualitative evaluation is thus made very difficult, and quantitative evaluation becomes impossible. In 'H spectroscopic analysis of xanthan, these problems occur at concentrations as low as 0,5 wt.-9'0. 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(acry1amide-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 the functional groups was observed in any of the polymers, and in the case of xanthan no cleavage of side chains occurred. In schizophyllan the triple helix structure also remained intact after degradation. It is postulated that degradation is attributed to elongational flow conditions produced by cavitation in ultrasonic fields.