Colloidal Lignin Valorization: From Macromolecular Design to Targeted Applications

Converting lignin into useful colloidal entities with uniform size and shape offers exciting opportunities for utilization; however, this endeavor requires overcoming challenges caused by structural heterogeneity and gaining further understanding to exploit its unique functional possibilities. Still, colloidal lignin has already provided new insights into bio-polymeric materials and has triggered various innovative applications that have inspired the scientific community. This review aims to provide a comprehensive discussion of the current understanding of colloidal lignin and its emergent applications. First, a fundamental overview of lignin, including its chemistry and processing is provided. Subsequently, a multitude of technical routes to tune the properties of colloidal lignin using nano-/micro-fabrication approaches to control macroscale properties is presented. Thereafter, examples of innovative material technologies based on colloidal lignin in areas such as pollution remediation, polymeric materials, macromolecular materials, and drug delivery are given. Finally, open challenges and suggestions for future research will be discussed to guide future research to rationally expand the portfolio of promising lignin-based technologies.