Lignin-Assisted Stabilization of an Oriented Liquid Crystalline Cellulosic Mesophase, Part A: Observation of Microstructural and Mechanical Behavior.

Liquid crystalline polymer blends containing lignin have been scarcely studied in the literature, albeit demonstrating potential for the design of high-performance lignin-based materials. In this study, organosolv lignin is blended in solution with hydroxypropyl cellulose (HPC), a lyotropic cellulose derivative, and its impact on the dynamics of the cellulosic liquid crystalline mesophase is investigated. Rheological measurements and rheo-optical investigations under crossed polarizers reveal that lignin enhances the persistence of the shear-induced orientation of the cellulosic macromolecules. In shear-cast films, the retention of the microstructural organization or band texture entails a drastic increase of the mechanical anisotropy and properties with lignin content. For the origin of the textural stabilization, we propose a specific "jacketing"-like effect of lignin on HPC. This study indicates the possibility of a beneficial impact of lignin on the relaxation behavior of liquid crystalline cellulosic polymers.