Organosolv Lignin-Based Electrospun Nanofibers: Stable Compositions and Morphological Insights

Lignin, a major component of lignocellulosic biomass, has been gaining interest as a sustainable alternative to petroleum-based polymers (e.g., polyacrylonitrile, PAN), and its valorization has included the production of nanofibers by electrospinning. In this work, we identify stable compositions leading to robust electrospinning from two different sources of organosolv lignin (OL), softwood (SOL), and hardwood (HOL), combined with variable concentrations of poly-(ethylene oxide) (PEO) of different molecular weights. Robust spinning of the solutions is sought while minimizing the required binder polymer and maximizing the lignin content in the produced fibers. The stability of the electrospinning process was rigorously monitored by imaging the Taylor cone (TC) during fiber formation by high-speed video, while solution rheology was analyzed to characterize the solutions and aid in understanding the fiber formation mechanism. The internal structure of the fibers was characterized by focused ion beam field emission scanning electron microscopy (FIB-FESEM), revealing the presence of internal voids in all compositions. When lignin was predominant, the fiber diameter was systematically smaller for HOL than for SOL, possibly due to the smaller molecular weight, revealing submicrometer fiber diameters in both cases. Finally, on the basis of these findings, a fiber formation mechanism is proposed.