New Insight into Industrial Lignin Intermolecular Force Heterogeneity Mitigation: Monodispersed Lignin Colloidal Sphere Synthesis and Full Biomass Photonic Material Preparation

Industrial lignin is an underutilized resource from the pulping industry due to its high heterogeneity. The transformation of industrial lignin into monodispersed lignin colloidal spheres (LCSs) for the preparation of advanced biomass photonic materials is particularly appealing, because of their unique biocompatibility. However, the LCSs synthesized from industrial lignin generally show a wide size distribution and thus limit this specific application. To address the issue, selective functionalization was carried out to convert phenolic and aliphatic -OH groups into ester groups, decreasing the LCS size distribution to a monodispersing degree. Simulation analysis revealed that the functionalization had narrowed the difference of C-O linkage electron cloud distribution and led to a lignin polarity decrease. Additionally, atomic force microscopy (AFM) quantification of lignin proved a force distribution index (FDI) decrease from 0.38 to 0.11, which was consistent with the LCS polymer dispersity index (PDI) decrease from 0.182 to 0.05. The photonic materials can be readily prepared from monodispersed LCSs with the color precisely adjusted by controlling LCS particle sizes.