Liquid crystalline solutions of cellulose in phosphoric acid

It was found that anhydrous phosphoric acid is an excellent direct solvent for cellulose. Dissolution is very fast, and liquid crystalline solutions are formed above a cellulose concentration of 7.5% (w/w) at room temperature; even solutions containing 38% (w/w) cellulose can be prepared. The composition of the solvent is expressed in a P2O5 concentration. Anhydrous conditions are obtained above a P2O5 concentration of 74% (w/w) (superphosphoric acid). The solutions were characterised by determining the clearing temperature, which was found to increase with decreasing water content in the phosphoric acid solvent and to level off under anhydrous conditions. Cellulose yarns with high moduli and high tenacities were wet spun from the anisotropic solutions. Superphosphoric acid is also capable of dissolving inter aliacellulose acetate, ethyl cellulose and chitin, with formation of anisotropic solutions.