Technical lignins, abundantly available as side streams from pulp industry and biorefineries, are challenging to valorize for purposes other than energy due to their recalcitrant and heterogeneous structure. One way to overcome this challenge is the self-assembly into of spherical, water-dispersable lignin nanoparticles (LNPs). LNPs hold tremendous potential due to their nano-scale morphology and well-defined surface characteristics. In high volume products like composites, adhesives, coatings and emulsions, LNPs can introduce better processability, compatibility, functionality or stability compared to other forms of lignin. Furthermore, the spherical morphology and tunable size enables applications in totally new fields for example drug delivery or cosmetics.

Despite that LNPs have been extensively studied for over ten years their formation mechanism is not fully understood and the current literature is partly contradictory. Here we aim to shed light on how interactions between lignin molecules and solvents affect particle formation and suggest some reasons for the contradictory theories. We will also demonstrate recent application utilizing LNPs, which vary from functional coatings to emulsion and foam stabilization. For example, fatty-acid functionalized LNPs were used for multifuctional textile coatings showing both excellent dirt repellence and breathability (1). The thin coating did not hamper the recycling of the textiles via spinning using Ioncell technology. Thicker coatings showed potential as bio-based barriers. Ultrathin, superhydrophilic, transparent LNP films were demonstrated as antifogging coatings (2). To determine the feasibility of the modified and unmodified LNPs their safety as well as their impact on product recycling and biodegradability were evaluated.