Mechanochemical Solid-Phase Dissolution of Cellulose and Synthetic Polymers in N-Methylmorpholine N-oxide and Its Use in Fiber Spinning

Academician N.S. Enikolopov’s method of mechanochemical solid-phase modification of polymers under conditions of intensive shear deformation has resolved one of the most important issues in cellulose processing, its dissolution. The resulting method of solid-phase dissolution in N-methylmorpholine Nрoxide (MMO) has afforded highly concentrated solutions of cellulose and a series of synthetic polymers, as well as mixed solutions based on them in a wide range of concentrations. It has been shown for the first time that the highly concentrated phase (cellulose concentration up to 45%) formed during phase separation in the presence of a precipitant undergoes a transition into nonequilibrium columnar mesophase state. The addition of synthetic polymers, which form crystal solvates with MMO but do not interact with cellulose, to solutions of cellulose in MMO shifts the columnar mesophase formation process into equilibrium. The resulting composite fibers have exhibited high strength and deformation properties. The mechanisms of interaction of various types of polymers with MMO, as well as these between cellulose and the polymers with MMO, at different stages of the mixed compositions preparation (from solid-phase mechanical activation during shear deformation to the transition into a fluid state and spinning) have been elucidated. The performed experiments have made it possible to identify the directions for targeted tuning of cellulose structure and properties, as well as the fabrication of compositions based on it.