Periodic Reporting for period 1 - CIRCULIG (Circular lignin materials from well-defined functional building blocks)
Reporting period: 2023-03-01 to 2025-08-31
Lignin is one of nature’s remarkable macromolecular materials, combining molecular complexity with properties that enable trees to grow upright and form robust, biochemically resilient structures. Yet in the forest industry, most lignin is simply burned, missing the potential to replace fossil-based resources. The CIRCULIG research aims to transform this status quo by pioneering circular lignin materials with advanced functionalities derived from precisely controlled nanostructures. These materials include, for instance, adhesives, catalysts, and vivid structural colors. Their synthesis and assembly demand significant advances in method development to overcome lignin’s inherent material limitations and to fully exploit its natural capabilities. This foundational work will unlock entirely new horizons for lignin-based materials. Beyond materials science, the broader impact spans promising interdisciplinary opportunities across environmental sciences, chemical and process engineering, and life sciences.
Our contributions to the field of lignin nanoparticles—particularly in the areas of stabilization and chemical functionalization—were published in our Account that demonstrated, for example, that fatty acid derivatives can be used to modify lignin, rendering it suitable for thermoplastic processing. This includes the production of meltspun microfibers that can be made magnetically responsive through the incorporation of magnetite nanoparticles. Circularity of the microfibers was demonstrated by their reuse as adsorbents for cationic dyes, followed by repeated melt spinning without desorption of the organic dye.
In another original research study, we showed that physical blends of the oriental lacquer Urushi with lignin can form hybrid nanoparticles with extended stability under both acidic and alkaline conditions. These hybrid particles are also attractive for surface modification applications, such as protective coatings for wood that were demonstrated in our article.
The CIRCULIG team also contributed to a Chemical Reviews article addressing circular aspects of polyesters. Poly(ethylene terephthalate) is one of the most common polyesters, used in a plethora of materials from beverage bottles to textile fibers. While current commodity polyesters do not contain lignin, our collaborative research has shown that lignin-based toughening additives hold great promise for improving the recyclability of PET plastics.
On the functional materials front, the development of photonic materials formed a key part of the original CIRCULIG research plan. We began this effort with fundamental studies on interparticle forces in colloidal systems and clarified how centrifugation can be used to classify particles into tightly packed layers exhibiting rainbow coloration. Building on this, we developed photonic glasses via a resource-efficient process using ethanol as a green organic solvent.
Finally, CIRCULIG research enabled the development of lignin gel emulsions recently demonstrated for environmentally benign hair conditioner formulations. These long-term stable emulsions can be directly prepared in micellar lignin nanogels by physically mixing in natural plant oils, such as sunflower or coconut oil, which act as the lubricating component. Mechanical force measurements showed that the hair conditioning performance was comparable to that of commercial off-the-shelf products.
In another original research study, we showed that physical blends of the oriental lacquer Urushi with lignin can form hybrid nanoparticles with extended stability under both acidic and alkaline conditions. These hybrid particles are also attractive for surface modification applications, such as protective coatings for wood that were demonstrated in our article.
The CIRCULIG team also contributed to a Chemical Reviews article addressing circular aspects of polyesters. Poly(ethylene terephthalate) is one of the most common polyesters, used in a plethora of materials from beverage bottles to textile fibers. While current commodity polyesters do not contain lignin, our collaborative research has shown that lignin-based toughening additives hold great promise for improving the recyclability of PET plastics.
On the functional materials front, the development of photonic materials formed a key part of the original CIRCULIG research plan. We began this effort with fundamental studies on interparticle forces in colloidal systems and clarified how centrifugation can be used to classify particles into tightly packed layers exhibiting rainbow coloration. Building on this, we developed photonic glasses via a resource-efficient process using ethanol as a green organic solvent.
Finally, CIRCULIG research enabled the development of lignin gel emulsions recently demonstrated for environmentally benign hair conditioner formulations. These long-term stable emulsions can be directly prepared in micellar lignin nanogels by physically mixing in natural plant oils, such as sunflower or coconut oil, which act as the lubricating component. Mechanical force measurements showed that the hair conditioning performance was comparable to that of commercial off-the-shelf products.
Lignin photonic glasses require further development to replace the energy-demanding centrifugation step used with a more scalable production technology. In parallel, the recycling aspects of lignin nanoparticle assemblies remain an active area of research within CIRCULIG, with promising potential for significant breakthroughs.
Our work on Urushi–lignin hybrid particles represents a notable contribution to the application of green chemistry principles in lignin-based materials. These functional nanoparticle dispersions were formulated entirely from biobased components, without the use of fossil-derived chemicals. Our collaborators have used oleate esters of softwood kraft lignin to improve the lightfastness of black urushi in aesthetically valuable wood coatings.
The lignin-based hair conditioner also requires further refinement, particularly to address aesthetic aspects—specifically, enabling color adjustability across light to dark brown shades. In addition, safety validation through skin and eye sensitization tests is essential. These activities could be advanced through an ERC Proof of Concept (PoC) project, which would also support commercialization via spin-off companies.
Our work on Urushi–lignin hybrid particles represents a notable contribution to the application of green chemistry principles in lignin-based materials. These functional nanoparticle dispersions were formulated entirely from biobased components, without the use of fossil-derived chemicals. Our collaborators have used oleate esters of softwood kraft lignin to improve the lightfastness of black urushi in aesthetically valuable wood coatings.
The lignin-based hair conditioner also requires further refinement, particularly to address aesthetic aspects—specifically, enabling color adjustability across light to dark brown shades. In addition, safety validation through skin and eye sensitization tests is essential. These activities could be advanced through an ERC Proof of Concept (PoC) project, which would also support commercialization via spin-off companies.