Research on Cellulose Morphology

Research is being conducted at the U. S. Forest Products Lab., Madison, Wis., to help resolve the question of diameter variation of elementary fibrils obtained from natural sources. Conflicting theories on cellulose morphology advanced in previous publications may well have been influenced by laboratory techniques and methods of specimen preparation. The geometry of cellulosic material is drastically altered from that of wood in its natural state to a dispersion of delignified cell wall material sufficiently fine to be observed in the electron microscope. It is important that the influence on elementary fibril diameter of chemical and physical forces of delignification, negative staining, drying stresses, and mechanical stresses imposed to effect geometrical reduction of cellulosic material be clarified. Material from one source is being delignified by different chemical methods and the resulting elementary fibril diameters are compared with those from nonlignified material, such as cottonseed hairs or Valonia fibers. Electron micrograph contrast has been achieved with phosphotungstic acid (PTA). Concentration of PTA and drying time will be studied for the beaded appearance described by Manley (1965) as well as for their influence on elementary fibril diameter. These results will be compared to fibril diameters observed with an electron microscope in the complete absence of PTA. Drying stresses of unknown magnitude introduced in removing water of staining solutions modify the intrinsic diameter of the elementary fibrils. This effect will be studied by variation of drying rate and by freeze drying.

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