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3.10 High-consistency colloidal lignin dispersions without organic solvents

Colloidal lignin particles present opportunities for bio-based materials, but the presently known preparation methods rely on organic solvents and energy intensive water evaporation processes. Here we present organic solvent-free production of colloidally stable lignin nanoparticle dispersions at concentrations above 40 wt% based on non-covalent assembly only. In contrast to the previously known methods, the size of the colloidal lignin particles does not increase, but instead decreases, with increasing lignin concentration. Based on TEM and cryo-TEM images the particles display characteristic features of soft nanoparticles resembling micelles. Their viscosity is concentration- and pH-dependent. Furthermore, these new type of lignin dispersion can be adjusted from free-flowing fluids to freestanding gels that are dryable and redispersible. These unique properties allow processing and formulation of lignin nanoparticles for example as composite filaments and foams. Overall, this new and facile method unlocks new scalable production routes towards sustainable lignin-based materials.