Development and relaxation of orientation in pure polymer liquid crystals and blends

Gedde, Ulf W.; Wiberg, G.

doi:10.1007/978-1-4615-5799-9_10

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“…Building on these studies, we recently demonstrated that organosolv lignin drastically stabilizes the shear-induced oriented structure of hydroxypropyl cellulose, the so-called band texture . The band texture is a well-known phenomenon for LCPs. − The bulk macromolecular relaxation of the elastic energy stored in the texture occurs in a sinoidal or zigzag manner and appears as a banded microstructure under crossed polarizers. − In our prior study, we revealed that the stability of the band texture was not only drastically increased by the presence of organosolv lignin but further allowed the manufacture of highly anisotropic “banded films” upon drying. In this way, blend films were prepared exhibiting an increase in modulus and tensile strength of up to 500% compared to pure HPC, i.e., values of 2.7 GPa and 60 MPa, respectively, for blend films containing 30% lignin (by weight).…”

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confidence: 90%

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

et al. 2020

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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.

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