Functional “permanently whitened” lignin synthesized via solvent-controlled encapsulation

Abstract

Here, we present a practical method for whitening lignin derivatives, which is solvent-controlled encapsulation (SCE) to rearrange the chromosphere at the solvent/lignin interface. Water, ethanol, and/or acetone are mixed to adjust the polarity of the solvent, resulting in lignin nanoparticles with hydrophobic chromophores within the core. Whitening lignin derivatives are produced when the hydroxy group is simultaneously modified by a non-chromophoric organic group. The SCE method is used in various organic isocyanates with different substituents and lignin derivatives. The whitened lignin nanoparticle acts as transmittance coating-film, glass/quartz adhesive, and heatproofing additive for poly(ε-caprolactam). Our results first demonstrate that lignin can be used as whitened polymers with high design flexibility and material functionality. A broad-range usage of lignin via its whitening is encouraged to realize conversion from oil-based refinery to biomass-based refinery.