Comparative study of samples of powdered and microcrystalline celluloses of different natural origins: Supermolecular structure and the chemical composition of powdered samples

Methods of wide-angle X-ray scattering (WAXS), high resolution solid-state ¹³C NMR, and Fourier transform IR-spectroscopy are applied to study supermolecular structures and functional compositions of lignocellulose samples of wood and grass origins and powdered celluloses (PC) obtained from them under identical hydrolysis conditions. It was shown by WAXS that the structure of cellulose I is preserved in samples of powdered celluloses, however, an increased degree of crystallinity and cross-section sizes of crystallites are observed in PC samples. Specific features of changes in the supermolecular structure of cellulose occurred after the hydrolysis, i.e., an increase in the content of cellulose I_β in PC compared to the initial samples, are established by ¹³C NMR method. It was shown by means of ¹³C NMR and Fourier transform IR-spectroscopy that the functional chemical composition of lignocelluloses is weakly affected by the hydrolysis. The presence of residual lignin functional groups in the samples is confirmed.