Molecular Weight of Native Cellulose

Abstract

THE molecular weight of cellulose is of great interest to cellulose chemistry, and many attempts have been made to determine it. The cellulose derivatives, esters and ethers, can in general be dissolved in simple organic solvents, and their molecular weights determined by the osmotic pressure method. It is questionable, however, if the derivatives can be prepared without degradation of the cellulose molecule. Therefore the study of cellulose in cuprammonium solutions is of very great interest. It has never been possible to carry out osmotic measurements of these solutions, owing to their high vapour pressure and the difficulties of membrane materials. Staudinger¹ has extrapolated his ‘viscosity rule’ from measurements of relatively low molecular weight materials and obtained degrees of polymerization of 2,000–3,000 for native cotton and ramie. Sedimentation equilibrium measurements were performed by Kraemer², who obtained values up to 1,300 for purified cotton linters, and estimated the molecular weight of native cellulose to be at least 570,000 (D.P. 3,500). Later, Mosimann³ showed that sedimentation equilibrium experiments with filament molecules (nitrocelluloses) of very high molecular weights give doubtful results owing to swelling-pressure effects.