Investigating the Structure–Size Relationship between Organosolv Lignin and Its Colloidal Particles

Due to lignin's complexity and heterogeneity, the influence of lignin structures on its nano or colloidal particle fabrication remains unclear. In this work, organosolv lignins representing a gradient of β-aryl ether linkage, phenolic OH groups, and molecular weights were extracted to fabricate size-tunable colloidal lignin particles (CLPs). DLS (dynamic light scattering) analysis revealed that the CLP size strongly correlates with the lignin structure and initial concentration. CLPs formed at low lignin concentrations (1 and 2.5 mg/mL) were smaller (200-400 nm), while higher lignin initial concentrations (10 and 20 mg/mL) yielded larger particles (500-750 nm). Lignin with fewer β-O-4 linkages, lower molecular weight, and higher phenolic OH content forms smaller CLPs at low lignin concentrations; in contrast, it tends to form larger CLPs at high lignin concentrations. The relationship between the CLP size and lignin typical structures provides new insights for fabricating size-tunable lignin particles with tailored applications.