Stretch-Induced Crystallization of Cellulose Spun from Ionic Liquid Solution

With the emergence of efficient green solvents, structural regulation of regenerated cellulose is highly desired in the solution process from an industrial perspective. Cellulose fiber and films are viewed as a "composite" comprising amorphous and crystalline fractions. The regulation of the crystalline structure is of great importance for the properties of cellulose materials. In this study, we found stretch-induced crystallization behavior during the transition from solution to gel via coagulation. The crystallinity index of the hydrogel fiber increases with the stretch ratio (SR). X-ray diffraction revealed that the cellulose II hydrate formed in the stretched hydrogel fibers. The mechanical properties and thermal stability of the dry fibers greatly improved against the SR. This crystallization behavior depends on the concentration of the solution and the type of ionic liquid. This stretch-induced crystallization provides an efficient method for structural regulation in cellulose solution processing.