Lignin’s structure has been noted in the literature to be optically inactive and amorphous by the absence of atomic symmetry. However, amorphous materials can undergo orientation and a few studies have previously shown preferred orientation of lignin in the native state. As molecular orientation can help enhance mechanical properties of fibers, electrospinning was used to produce nano- to sub-micron scale fibers of lignin. In this process, final microstructure and properties of electrospun fibers are governed by the simultaneous solvent evaporation and rapid elongation of the solidifying fiber jets on a very short time range (&lt; 0.5 µs), thus providing the possibility to orient molecules along the fiber axis. In this study, the orientation of softwood kraft lignin within the aligned fiber mats was evaluated by polarized light optical microscopy (POM) with a rotating polarizer. Furthermore, the functional groups of lignin that had preferred alignment along the fiber axis were identified with polarized FTIR indicating orientation based on dichroism measurements. In addition, nanocrystalline cellulose (NCC) was added into lignin and the impact of these nanoscale additives on the orientation of lignin molecular chains within the aligned fibers was also investigated utilizing polarized FTIR analysis. This approach provided insight on the alignment of these nanoadditives along the fiber axis, as well if they further induced orientation of the lignin. Further, solvent cast lignin films were analyzed for their anisotropic polarizability resulting in birefringence in the cast films of lignin with and without NCC. Therefore, this talk provides insight into molecular orientation and organization of lignin and additional insight into the alignment of nanoscale additives in solvent-processed materials.

Is it possible for lignin molecules to become oriented during processing?

2019 Spring National Meeting

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