Crystalline Forms of Cellulose in Softwoods and Hardwoods

Abstract

Resolution-enhanced ¹³C 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 Iα and Iβ 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.