CRYSTALLINE FORMS OF CELLULOSE IN SOFTWOODS AND HARDWOODS

Resolution-enhanced C-13 CP/MAS NMR spectra were obtained for woods from 7 different tree species. Ratios of signal strengths at 90.2 and 88.6 ppm were used to estimate relative proportions of I alpha and I beta crystalline forms of cellulose. These ratios were distinctly higher for softwoods than for hardwoods. The NMR results therefore support published X-ray diffraction evidence for differences between crystalline forms of cellulose in softwoods and hardwoods. Resolution of signals at 84.0 and 84.9 ppm provided evidence for a high degree of molecular order on the surfaces of cellulose crystallites in wood.