Multifunctional, Flexible, Electrospun Lignin/PLA Micro/Nanofiber Mats from Softwood Kraft, Hardwood Alcell, and Switchgrass CELF Lignin

Herein, biobased 1:1 lignin/polylactic acid (PLA) blends are electrospun into micro- and nanofiber mats. Lignin samples originating from softwood, hardwood, and switchgrass biomass, extracted through the Kraft, Alcell, and CELF processes, respectively, and processed into soluble and insoluble fractions, are used. Functional properties of the mats varied with lignin biomass origin, isolation method, and fraction. Mat attributes are demonstrated through analysis of spinnability, thermal and mechanical behavior, chemical structure, morphology, hydrophobicity, and antioxidant activity. Samples spun with hardwood Alcell lignin fractions were brittle and rigid with the highest Young’s modulus, lowest elongation at break, and hydrophobic contact angle > 100°. Switchgrass CELF lignin (SGL)/PLA mats showed the highest tensile strength, a low Young’s modulus, and high elongation at break, as well as good spinnability with the smallest fiber diameter from all samples. Kraft lignin/PLA demonstrated similar mechanical properties to SGL/PLA, as well as the highest antioxidant activity, measurable within 5 min. Therefore, while they did not dictate spinnability, the lignin biomass origin and pretreatment method were shown to have a significant impact on fiber properties, while the use of lignin fractions was shown to tailor functional properties of fibers for specific end use, such as in flexible, hydrophobic, or antioxidant product applications.