Development and evaluation of methods for determining the pattern of functionalization in sodium carboxymethylcelluloses

Abstract

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.

Detailed investigation on the molecular structure of carboxymethyl cellulose with unusual substitution pattern by means of an enzyme-supported analysis

“…The method was confirmed by liquid and solidstate NMR techniques. [14] High pH anion exchange chromatography with pulsed amperometric detection (AEC-PAD) can separate glucose and the 7 carboxymethyl glucoses (CMG). [15] Analysis was performed as described previously.…”

The influence of fibre wall thickness on the undissolved residuals in CMC solutions

“…An organic slurry medium or solvent is applied, and this influences the reaction and the structural features of the product (Liebert and Heinze 2001;Olaru and Olaru 2001). Various methods have also been developed to determine the functionalisation pattern of CMC (Heinze et al 1994;Ka¨uper et al 1998;Horner et al 1999;Saake et al 2001).…”

Synthesis and13C CP MAS NMR spectroscopy of cellulose-graft-poly(N-acetylethylenimine)

“…[19] There have been few reports on the quantitative analysis of 13 C CP MAS spectroscopy in junction with cellulose derivatives. Käuper et al [12] recently reported on the quantitative analysis of carboxymethyl cellulose via 13 C CP MAS NMR spectroscopy by monitoring the relaxation process of the individual carbon resonances by variation of the Hartmann Hahn contact time and found results which were in excellent agreement compared to conventional quantification methods. Cook et al [21] relied on the use of a ramp CP pulse technique to correct for the narrow Hartmann Hahn match due to the high spinning frequency.…”

“…Thus the grafting efficiency could be controlled by the DS Tos of the starting tosyl celluloses, whereas the amount of monomer showed only a minor influence on the grafting density. small fragments and the subsequent identification by chromatographic methods is applied, [12] sometimes leaving open if grafted polymer chains have been cleaved off the cellulose backbone during this procedure.…”