C-13 solid-state NMR determination of cross-linking degree in superabsorbing cellulose-based networks

C-13 solid-state NMR analysis has been performed on microporous superabsorb ing networks based on hydroxyethylcellulose and sodium salt of carboxymethy lcellulose in order to determine the chemically effective cross-linking deg ree. Microporous samples characterized by two different degrees of cross-li nk have been analyzed by performing C-13 cross-polarization magic angle spi nning (CP-MAS) solid-state spectra and single-pulse excitation (SPE) experi ments. Cross-linking degrees, expressed as number of cross-links per monome r, have been evaluated from the area of resonance due to methylene carbon a toms present on reacted cross-linker molecule (divinyl sulfone) and area of resonances due to anomeric carbon atoms C-l of the polysaccharide rings. O ptimization procedures for both CP-MAS and SPE experiments are also reporte d.