Structural differences between non-wood plant celluloses: evidence from solid state NMR, vibrational spectroscopy and X-ray diffractometry

Cellulose from flax, hemp, kenaf and sorghum was investigated by solid stat e NMR and vibrational spectroscopy, and the structural differences found we re validated by X-ray diffractometry. All three techniques indicate a notab le region of order in the cellulose of both Bar and hemp, but the absolute crystallinity values are not directly comparable. CP-MAS C-13-NMR and FTIR spectroscopy revealed the presence of I alpha and I beta forms in all the s amples. On passing from flax and hemp to kenaf and sorghum the progressive loss in the crystalline phase is evidenced by C-13-CPMAS T-1 measurements; H-1-CPMAS T-1 rho measurement revealed an analogous loss in phase dimension for the ordered phase, but similar dimension values for the paracrystallin e and amorphous phases. The FTIR and FTRaman spectra of all the cellulose s amples reveal the same chain conformation but a different hydrogen bond pat tern, and this accounts for the NMR and X-ray results. (C) 2001 Elsevier Sc ience B.V. All rights reserved.