Supramolecular room-temperature flowable lignin (RTFL)/MXene for sustainable coatings

Thermoelectric coatings with high biomass content, excellent storage stability, and solvent-free curing capabilities are highly desirable yet challenging. In this study, we demonstrate that supramolecular room-temperature flowable lignin (RTFL) was introduced as an effective carrier for the two-dimensional conductive material MXene, facilitating the development of supramolecular sustainable coatings. Lignosulfonic acid (LA) and polymerizable quaternary ammonium salt monomers were successfully utilized to synthesize the RTFL with ultra-low glass transition temperatures (-67--38 °C) using a deep eutectic strategy, with lignin content reaching up to 50 wt% without relying on traditional solvents. The RTFL demonstrated, serving as a macromolecular solvent, effectively dispersing and stabilizing MXene while preventing long-term oxidation. When directly coated onto various substrates and subsequently subjected to rapid photopolymerization, the RTFL/MXene coating exhibited remarkable photo-thermal-electric conversion properties. These features meet the requirements of various electrical applications, including Stirling engines and battery charging lamps. This supramolecular approach offers a pathway for developing high biomass content coatings suitable for environmental and energy-related applications.