Chapter 10. Near Infrared Spectroscopic Monitoring of the Diffusion Process of Deuterium-Labeled Molecules in Wood

摘要

Near infrared transmission spectroscopy was used to monitor the diffusion process of deuterium-labeled molecules in wood samples. To better understand the state of order in wood cellulose, several diffusion experiments were performed with Sitka spruce and beech in D_2O and two OD-deuterated alcohols of different geometry. Four absorption bands in the NIR region (7200-6100 cm~(-1)) were assigned to 2 x v (OH) absorptions of OH groups in the amorphous, semi-crystalline, and the two kinds of intramolecularly hydrogen-bonded crystalline regions, respectively. The saturation accessibility varied characteristically with the OH groups in different states of order in the wood substance, the diffusants, and the wood species, respectively. The effect of the anatomical cellular structure on the accessibility is reflected in the variation of the diffusion rate with wood species. We proposed a new interpretation about the fine structure of the microfibrils in the cell wall by comparing a series of results for hardwood and softwood specimens.