Investigation of wet spinning conditions of cellulose derivatives to prepare structure colored fiber with cholesteric liquid crystal

Cellulose derivatives forming a cholesteric liquid crystal (CLC) structure under a room condition were synthesized via the esterification of hydroxypropyl cellulose (HPC) with propionic anhydride. Structural colored fibers were spun by wet spinning from the acetone solution of these cellulose derivatives to water as a coagulation bath and liquid-crystallizing by removing water in the fiber under controlled humidity. However, the fiber cross section was crescent-shaped with a deformation in the drying process, because it was not coagulated enough due to the high affinity between water and the cellulose derivative. The Hansen Solubility Parameters (HSP) of the cellulose derivative was calculated by using HSPiP software and we selected diisobutyl ketone as a coagulation solvent with low affinity to the cellulose derivative and is miscible with acetone based on the relationship among each SP of components. In addition, diisobutyl ketone is a non-aqueous solution and it has a lower density than water. When the fiber was spun with the coagulation bath separated into two phases from water and diisobutyle ketone, the fiber was held at the interface between water and diisobutyl ketone, and it was coagulated well to form a round cross section. After the drying process, the obtained fiber exhibited structural color and its morphology with the round cross section was stable.