Researchers have unveiled a groundbreaking method for creating room temperature phosphorescent (RTP) materials from lignin, the most abundant natural aromatic polymer, derived from biomass resources. Utilizing 2-hydroxyethyl acrylate (HEA) and urethane dimethacrylate (UDMA), this innovative approach operates without solvents, addressing the environmental issues associated with traditional lignin disposal.
This new solvent-free method is particularly timely, as approximately 60 to 70 million tons of lignin are produced annually, with around 95% of it being incinerated. By converting lignin—a byproduct typically discarded—into valuable phosphorescent materials, researchers aim to offer sustainable solutions to managing lignin waste and creating functional materials.
The collaborative study, published on March 12, 2025, describes how lignin, when mixed with HEA, forms stable solutions due to extensive hydrogen bonding. Upon exposure to ultraviolet (UV) light, the mixture generates radicals, instigates polymerization, and produces durable RTP materials. The resulting polymer network not only enhances the rigidity of lignin but also activates its humidity and water-resistant phosphorescent properties, achieving an impressive afterglow life of 202.9 milliseconds.
This material's mechanical properties are noteworthy, exhibiting tensile strength of 52.8 megapascals and elongation at break of 9.8%, thereby surpassing traditional products. The blend demonstrates significant viscosity and glass transition temperature of 68 degrees Celsius, which marks its adaptability for thermal processing.
Further experimentation showed the hybrid polymer (Lig-Poly) maintained its phosphorescent properties even under damp conditions, sustaining its luminescence when exposed to 90% humidity for 24 hours or immersion in water. This resilience adds substantial practicality for applications across diverse sectors.
One fascinating aspect of the research is its ability to modify the emission color of the phosphorescent material by loading it with Rhodamine B (RhB). This process utilizes energy transfer, leading to distinct color transformations with red afterglow emission properties boasting lifetime measurements of 167.7 milliseconds. The authors noted, "The obtained polymer network confined lignin and triggered green RTP emission from lignin with a lifetime of 202.9 ms, showcasing remarkable longevity and color tunability."
The innovative Lig-Poly materials have potential applications beyond mere aesthetic attributes; they can serve as photocured inks, luminescent coatings, and even function as sophisticated anti-counterfeiting logos for pharmaceutical products. This could revolutionize packaging, security, and anti-counterfeiting protocols.
Energy transfer efficiency between lignin and RhB increased impressively from zero to 30.4% at specific concentrations, illustrating the versatility and tunable nature of the developed system. This finding not only advances material science but encourages future explorations of similar sustainable methodologies.
The development marks considerable progress, merging ecological consciousness with technological innovation. The study exemplifies how addressing environmental issues related to lignin waste can yield high-performance materials beneficial for applications ranging from consumer products to industrial coatings.
Looking forward, the researchers are optimistic about broad manufacturing capabilities using Lig-Poly and similar materials created from readily available renewable resources. Such advancements resonate within the wider scope of sustainability trends, offering pathways toward developing significant and functional RTP materials for multiple use cases, especially as markets increasingly favor environmentally friendly products.