Advanced Characterization of Lignin Nanoparticles by Asymmetric Flow-Field Flow Fractionation

The unique properties of lignin nanoparticles (LNPs) - uniform shape, surface charge and nanoscale - carry great potential for the desired material utilization of technical lignins. Especially, the particle size distribution and dispersity of LNPs are the key for their successful valorization. However, characterization of LNPs usually requires a rather elaborate combination of light scattering and microscopy techniques which moreover provide only average values, are often limited in sampling size and require tedious sample preparation. Here we introduce a method based on asymmetric flow field-flow fractionation (AF4) coupled with multi angle laser light scattering (MALLS), dynamic light scattering (DLS) and refractive index (RI) detection for the analysis of size and shape of LNPs. Exploiting the separation power of AF4 in combination with MALLS, DLS, and RI allowed us to obtain enhanced particle size distributions of LNP that are comparable to batch DLS and AFM measurements. Moreover, we discuss the influence of the particle size on the MALLS and DLS signals and determination of the shape factor ρ of LNPs.