Characterization of cellulose and cellulose derivatives by high resolution solid state 13C-NMR-spectroscopy

An overview is given with regard to the possibilities of the solid-state C-13 NMR spectroscopy in characterizing cellulose structures. The techniques (cross-polarization, magic angle spinning) necessary for the measurement of high-resolution solid state 13C NMR spectra are introduced. The C-13 CP/MAS NMR spectrum of cellulose I is discussed as an example with regard to the assignment of the lines, line shape and spectral resolution. The influence of the super-molecular order on the spectrum and relations between line intensity and molecular dynamics are demonstrated. By applying appropriate experimental conditions structural components of solid-state cellulose with different chain mobility (e.g, crystalline, amorphous) can be determined. As shown with diethylaminoethylcellulose, the solid-state cellulose matrix and the liquid-like phase of substituents can be analyzed selectively by NMR. Furthermore, a survey of the spectra of the most important crystalline modifications of cellulose is given and methods for the quantitative phase analysis are demonstrated. By means of C-13 CP/MAS NMR, the formation of complexes or lattice modifications of cellulose with amines such as 1,2-propanediamine, 1,3-propanediamine or diethylenetriamine is proven. Finally, the characterization of the composition of solid state cellulose derivatives is discussed. In this respect the proof of a structure-selective, block-like carboxymethylation of cellulose is given.