Multidimensional Analyses for Testing Ecological, Ethnobiological, and Conservation Hypotheses

Abstract

Cellulose swells in different solvents. The extent of swelling depends on the solvent as well as on the nature of the cellulose sample. In the case of native cellulose with fibrous structure more or less drastic morphological changes take place depending on whether the swelling is interfibrillar or intrafibrillar. More generally the differences caused are distinguished in terms of intercrystalline and intracrystalline swelling. In the former case the swelling agent enters only into the disordered (amorphous) regions of cellulose microfibrils and between them, whereas in the latter case the ordered (crystalline) regions are penetrated. When bone-dry cellulose fibers are exposed to humidity, they adsorb water and cross section of fibers is increased because of swelling. At 100 % relative humidity this swelling corresponds roughly to a 25 % increase in the fiber diameter. An additional 25 % increase in swelling takes place when the fibers are immersed in water. In the longitudinal direction the dimensional change is very small. There are, on the other hand, many liquid solutions of strong acids, strong bases, and a few salts that determine an intracrystalline swelling, which change the X-ray patterns. From these one of most important reagent is sodium hydroxide which is used to improve the physical and chemical properties of cellulose. The swelling of cellulose in sodium hydroxide solution is a result of hydrated ions penetration, which requires more space than the water molecules. Alkali is not capable of dissolving native cellulose, but only to depolymerise cellulose fragments with low degree of polymerization. Also, the