Four carboxymethyl cellulose samples derived from the synthesis concept of “reaction in reactive microstructures” were characterised in detail by combination of different analytical techniques. Fractionation of one of the samples according to water‐solubility into four fractions revealed that a non‐statistical distribution of the substituents occurred for all fractions. Endoglucanase fragmentation of three samples was performed followed by analytical and preparative SEC. The multi‐detected analytical SEC proved samples of high degree of substitution up to 1.9 to be intensively degraded, supporting the proposed block‐like substitution pattern. The detailed investigation of soluble fragmentation products by preparative SEC, hydrolysis and anion exchange chromatography with pulsed amperometric detection revealed that all samples contain fragments of much higher DS values than the average DS of the starting material. On the other hand, high quantities of degradation products of low DS or almost no substitution occurred. Therefore, a structure can be proposed with segments of very high DS alternating with areas of limited substitution. The result clearly showed that the high substituted fragments were dominated by 2,3,6‐tri‐O‐CMG.

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Sodium carboxymethylcellulose (NaCMC) with varying degrees of substitution (DS) was investigated with different analytical methods in order to characterize the functional group distribution. The following methods were tested and adapted: high‐resolution 13C NMR spectroscopy in the solid state (13C CP/MAS NMR) and 13C NMR spectroscopy on solutions of NaCMC samples with a reduced molar mass. Partial degradation was accomplished by ultrasonic means and with the enzyme endoglucanase. Combining the two techniques resulted in the greatest reduction in molar mass and hence in the best spectral resolution. Analysis of the NaCMC fragments following ultrasonic and/or endoglucanase degradation also reveals another interesting experimental finding. It appears that ultrasonic degradation is favored at unsubstituted areas near the center of the chain. These methods were compared with the following already familiar techniques of analysis: titrimetric techniques; 13C and 1H NMR spectroscopy as well as HPLC on completely hydrolysed solutions (hydrolysis with perchloric acid, trifluoroacetic acid and sulfuric acid). All of the methods characterize the samples as a series with increasing DS, the values of which range from 0.9 to 2.4. Methods that permit analysis of the partial degree of substitution produced the distribution x2 > x6 > x3. Therefore, they are in principle suited for determining the functionalization pattern of the NaCMC samples relative to one another. The most suitable method can therefore be selected according to the objectives and the apparatus available. However, the measured values do exhibit considerable spread, variances of approx. 20%, thus, place restrictions on using the values of DS or xi in absolute comparisons beyond these methods.

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