FORMATION AND PROPERTIES OF THE LYOTROPIC MESOPHASE OF THE CELLULOSE MIXED INORGANIC ACID SYSTEM

As an extension of a previous study [K. Kamide, K. Okajima, T. Matsui, and S. Kajita, Polym. J., 18, 273 (1986)] on lyotropic mesophases of cellulose derivatives in aq. inorganic acid systems, the lyotropic mesophase of cellulose was studied in a mixture of sulfuric acid (SA)/polyphosphoric acid (PPA)/water (W). It was found that SA/PPA/W mixture with a specific composition (SA/PPA/W = ca. 1/8/1, w/w/w) gave mesophase solution of cellulose. The mesophase had a cholesteric nature as detected by circular dichroism and the cellulose in the system was not derivatized over the whole range of storage time (less than 48 h). A Raman spectroscopic study of the solvent mixtures revealed that the hydrolysis of polyphosphoric acid may be restricted in specific composition. Polarized IR study clarified that C-O stretching vibrations of the cellulose molecules in the film, cast from the mesophase solution. are oriented perpendicularly to the shear direction imposed on the mesophase in its film casting process. This phenomenon was not observed for the films prepared from isotropic solution of the same system.