Poly(Lactide)-Modified Lignin Nanofibers: Investigating the Role of Polymer Tacticity on Fiber Properties and Filtration Efficiency

Abstract

Lignin-graft-PLLA and lignin-graft-PDLA copolymers were synthesized and transformed into nanofibers through electrospinning. The nanofibers generated with either lignin-graft-PLLA or lignin-graft-PDLA showed X-ray diffraction (XRD) patterns corresponding to the homocrystallites of isotactic poly­(lactic acid) (PLA), whereas the nanofibers generated with 1:1 v/v solution blend of lignin-graft-PLLA/lignin-graft-PDLA showed stereocomplexation of the PLA chains. The stereocomplexation enhanced Young’s modulus from 212 and 298 to 469 MPa and tensile strength from 3.6 and 3.7 to 6.6 MPa, although sacrificing elongation at break. The lignin-graft-PLLA and lignin-graft-PDLA nanofibers showed quality factors of greater than 42 and 71 kPa–1, respectively, as potential lignin-based aerosol filters, yet the stereocomplexation was disadvantageous because of brittleness, interfiber fusion, and high pressure drop of above 103 Pa. We compare E-factors for this process and other similar systems and investigate fiber formation in ethyl acetate, a sustainable solvent.