Lignin-Assisted Stabilization of an Oriented Liquid Crystalline Cellulosic Mesophase, Part B: Toward the Molecular Origin and Mechanism

Abstract

Lignin valorization has been scarcely considered in the form of liquid crystalline polymer blends. Recently, a stabilizing effect of organosolv lignin (OSL) on the oriented mesophase of hydroxypropyl cellulose (HPC) was observed and related to drastic improvements in tensile properties of the blends. With a view to elucidating this relaxation phenomenon, different molecular weight fractions and derivatives of organosolv lignin are synthesized, blended in solution with the liquid crystalline cellulosic polymer and analyzed in regard to their effect on the microstructural evolution of shear-aligned HPC chains. The rheological and rheooptical investigations suggest a crucial contribution of the lower molecular weight oligomers and the phenolic hydroxy functionalities to the stabilization of the oriented cellulosic mesophase. The results provide an indication of the molecular origin and mechanism and might be of special interest for the production of anisotropic materials from liquid crystalline cellulosic polymers.

Lignin in Bio-Based Liquid Crystalline Network Material with Potential for Direct Ink Writing

“…Because of the ability of a liquid crystalline polymer (LCP) to serve both as processing aid and reinforcement, solution blending rod-like polymers with flexible coil polymers represents an established and potent approach to design strong lightweight molecular composites. − Within the current context of material sustainability, a renewed interest for LCPs blended with bio-based or biogenic polymers has recently emerged. , Concurrently, bio-based lyotropic polymers such as cellulose derivatives are revisited. − Building upon the efforts of Glasser and his co-workers − at adding value to lignin, the second most abundant biopolymer on earth, the potential of organosolv lignin (OSL) dispersed in the lyotropic phase of hydroxypropyl cellulose (HPC) for material design could be evidenced recently. , Interestingly, lignin was found to significantly improve the stability of the shear-induced transient band texture enabling the manufacture of highly oriented films via shear casting . The observed phenomenon was ascribed to enhanced miscibility and secondary intermolecular interactions between low molecular weight, phenolic OH-rich lignin fractions and HPC . According to the loading direction, the anisotropic banded HPC/OSL films behave as strong materials or as ductile materials paving the way to the design of high-performance architectured materials from bioresources .…”

“…7−9 Building upon the efforts of Glasser and his co-workers 10−13 at adding value to lignin, the second most abundant biopolymer on earth, the potential of organosolv lignin (OSL) dispersed in the lyotropic phase of hydroxypropyl cellulose (HPC) for material design could be evidenced recently. 14,15 Interestingly, lignin was found to significantly improve the stability of the shearinduced transient band texture enabling the manufacture of highly oriented films via shear casting. 14 The observed phenomenon was ascribed to enhanced miscibility and secondary intermolecular interactions between low molecular weight, phenolic OH-rich lignin fractions and HPC.…”

“…14 The observed phenomenon was ascribed to enhanced miscibility and secondary intermolecular interactions between low molecular weight, phenolic OH-rich lignin fractions and HPC. 15 According to the loading direction, the anisotropic banded HPC/OSL films behave as strong materials or as ductile materials paving the way to the design of high-performance architectured materials from bioresources. 16 However, owing to the water solubility of the HPC matrix polymer, the field of the application of the anisotropic HPC/OSL blend material is limited.…”

3D printing of lignin: Challenges, opportunities and roads onward

“…Lignin stabilizing effect in this blend was further found to stem from its phenolic‐OH groups and low molecular weight fraction, which enhanced lignin miscibility with HPC. [ 52,53 ] The anisotropic swelling imparted by molecular orientation and the resulting band texture formation endowed parts with morphing properties upon exposure to humidity, paving the way to the manufacture of sensing and soft robotic devices from fully bio‐based lignin systems. However, dragging of the outer layers to the center during printing limited dimensional stability and restricted the design space to continuously‐printed structures such as rings.…”

Direct Ink Writing of Fully Bio-Based Liquid Crystalline Lignin/Hydroxypropyl Cellulose Aqueous Inks: Optimization of Formulations and Printing Parameters

“…Further, for the corresponding organosolv lignin/HPC shear cast blends, excellent mechanical properties (E = 3.5 GPa; strength >80 MPa) have been ascribed to the shear-induced and lignin-stabilized band texture of HPC, a characteristic oriented morphology for liquid crystalline polymers. 51,52 As shearing also occurs during DIW, it can likewise be expected to induce molecular orientation, band texture, and thus high mechanical properties in direct ink written organosolv lignin/HPC inks. Altogether, direct ink writing inks of organosolv lignin/HPC blends might open new high-volume value-adding routes to lignin into high-performance anisotropic bio-based materials.…”