Estimation of the Relative Proportions of Cellulose I alpha and I beta in Wood by Carbon-13 NMR Spectroscopy

Summary Relative proportions of cellulose in the I α and I β molecular packing forms were estimated through a relationship between molecular packing and the center of gravity of a 13 C NMR signal assigned to C-4 of cellulose. An alternative method, based on generation of linear combinations of spectra of 2 samples of wood, was too time-consuming for routine use but provided data for calibration purposes. NMR spectra of algal, tunicate, bacterial and commercial fibrous-powder cellulose were also used for calibration purposes. Mass fractions of the I α form were estimated as 0.51 for Pinus radiata wood and 0.25 for Castanea sativa wood. The difference is too small to have an important effect on moduli of elasticity.