Nuclear magnetic resonance spectroscopic characterization of carboxymethylcellulose

Abstract

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.

Water-soluble binders for MCMB carbon anodes for lithium-ion batteries

“…The peak at ı 82.44 corresponds to C 4 and the peak at ı 102.71 belongs to C 1 . More importantly, the 13 C NMR peak that appeared at ı 178.13 corresponds to the COO-group [26,37] and thus confirms that the LiCMC has been successfully synthesized. For comparison purposes, NaCMC (Calbiochem) was also analysed by 1 H NMR and 13 C NMR and the same peaks were observed.…”

Effective Approaches for Estimating the Functionalization Pattern of Carboxymethyl Starch of Different Origin

“…The determination of the pattern of functionalization of polysaccharides on the level of the AGU is usually carried out by NMR spectroscopy [9,10,13]. This can either be done by 13 C-NMR spectroscopic measurements on the intact polymer or by 1 H-NMR spectroscopy on the hydrolytically degraded sample.…”

“…The 1 H-NMR analyses were carried out as described [13] prepared using a new synthesis concept via a reactive microstructure revealed a high DS achieved in a one-step synthesis as well as a nonstatistic distribution of carboxymethyl groups along the chain. A significant amount of 2,3,4,6-tetra-O-functionalization, caused by the branched structure of starch, was found.…”

“…By comparison of the measured values with those obtained by statistic calculations the distribution of the functional groups along the polymer chain can be evaluated. Combination of these results with 1 H-NMR analyses on depolymerized samples gives a fairly complete picture of the functionalization pattern [13,14]. These investigations are directly related to ongoing work on the search for alternative paths of polysaccharide etherification leading to derivatives with new patterns of functionalization.…”

The effect of carboxymenthyl cellulose in PP fibers for dye absorption ability

“…It has a number of sodium carboxymethyl groups (CH 2 COONa), introduced into the cellulose molecule, which promote water solubility. The three parameters that control the various properties of CMC are as follows; molecular weight of the polymer, average number of carboxyl content per anhydroglucose unit, and the distribution of carboxylmethyl group substituents along the polymer chains [5][6][7] During the past few years, many researchers have paid considerable attention to the study of carboxymethyl cellulose due to this material is an important industrial polymer which give a wide range of applications such as drag reduction, detergents, textiles, paper, foods, adhesives, paints, pharmaceutics, and oil well drilling operation. [8][9][10][11][12][13][14][15] In textiles industrial, CMC is used in the printing paste as a thickener and a emulsifier which significantly improve the vividness of printing, and improve the stability of the color paste.…”