Electron microscope investigations on fibril formation

In order to gain a better understanding of the formation and structure of natural fibrils as found in cellulose, chitin, etc., transitions from coils into fibrillar solid structures were investigated with some suitable polymers as model substances. Preliminary precipitation experiments of cellulose out of solution yielded no clear results. With cellulose tricarbanilate, rod‐like single molecules or single crystals with folded chains are formed at low concentrations and fibrils of different diameter with preferentially extended chains at higher concentrations. The results are discussed in terms of nucleation and chain stiffness. In the amylose iodine complex the transition from coils to fibrils with a uniform diameter of 40 Å could be shown. Alcohol complexes yielded only single crystals. With mannan and cellulose tribenzoate ribbon‐like fibrils are found. Trimethyl cellulose finally formed fibrils with a uniform diameter of 200 Å and a helical periodicity of 200 Å along the chain. On the basis of the above‐mentioned results a modification of Manley's model of the cellulose elementary fibrils is proposed and discussed in relation to properties and biosynthesis of cellulose.