Understanding the impact of lignin-derivable non-isocyanate polyurethane (NIPU) chemistry on electrospinnability and fiber quality

Abstract

Polyurethanes (PUs) are a critical component of the global polymer industry but mainly are derived from fossil fuels and contain hazardous precursors. Non-isocyanate polyurethanes (NIPUs) derived from lignocellulosic biomass, not only provide a safer and sustainable alternative to conventional PUs but also contain functional groups that can alleviate processing challenges and improve electrospinnability. In this work, lignin-derivable bisguaiacol A (BGA)-NIPU (one methoxy group on each aromatic ring with dimethyl bridging substitution) and bisguaiacol F (BGF)-NIPUs (one methoxy group on each aromatic ring without dimethyl bridging substitution) are used to fabricate electrospun fiber mats; and the impact of lignin-derivable NIPU chemistries on electrospinnability and fiber quality is studied. It was found that the presence of methoxy groups in lignin-derivable NIPUs led to a 10-50% increase in viscosity as compared to the bisphenol A (BPA)-NIPU control (no methoxy groups with a dimethyl substitution). Additionally, the absence of dimethyl substitution led to the highest viscosity and completely bead-free fibers in BGF-NIPU in comparison to BPA-NIPU and BGA-NIPU. This work provides an understanding of structure-processing relationships for the electrospinning of lignin-derivable NIPUs. These insights can help inform future studies regarding manufacturing of bio-based NIPU fibers and fiber-composites for different applications.