Lignin Containing Cellulose Nanofiber Based Nanopapers with Ultrahigh Optical Transmittance and Haze

In this study, lignin containing cellulose nanofiber/glycerol (LCNF/Gly) composite films at different mixing ratios were developed with LCNFs extracted from commercial poplar pulp through 2,2,6,6-tetramethylpiperidine-l-oxyl radical (TEMPO) mediated oxidation followed by high-pressure homogenization. The obtained LCNFs with the diameters ranged from several to tens of nanometers, were decorated with residual hydrophobic lignin nanoparticles (16.31 wt%) around the nanofibers, and showed the reversible aggregation in aqueous solution. With the incorporation of glycerol, the resulting LCNF/Gly films exhibited excellent light management properties, maintaining outstanding optical transmittance (87%) and ultrahigh haze over 92%, with superior ultraviolet (UV) blocking function for UVB and UVC. Meanwhile, the brittleness and fragility of the LCNF/Gly films are greatly reduced and the elongation at break of the films are increased from 1.58 to 7.48% with the increase of glycerol mass ratio, endowing the composite films excellent ductility for applications in food packaging, solar cell, anti-glare film and flexible optoelectronic devices.