Elschner Thomas, Schönrich Jakob, Bračič Matej, Maver Tina, Maver Uroš, Fischer Steffen
Institute of Plant and Wood Chemistry, Dresden University of Technology, Pienner Str. 19, 01737, Tharandt, Saxony, Germany.
Faculty of Mechanical Engineering, Institute of Engineering Materials and Design, University of Maribor, Smetanova 17, 2000, Maribor, Slovenia.
Sci Rep. 2025 Sep 12;15(1):32471. doi: 10.1038/s41598-025-18530-9.
The chemical recalcitrance of lignin limits the industrial processing of biomass, which could be addressed by so-called designer lignins. Dehydrogenation polymers (DHPs) formed by artificial lignification of monolignols, enable studies on structure-property relationships independently of genetic information. Thin films of phenolic acid esters of cellulose were prepared and used for quartz crystal microbalance with dissipation monitoring (QCM-D) experiments to investigate surface polymerization in real-time. The phenolic anchor groups significantly influenced lignification speed, deposited mass, and rigidity of resulting DHP layers. Linkage types in the lignin structure were quantified by HSQC NMR spectroscopy. Polymerization efficiency was increased in the order ferulate < p-coumarate < caffeate. Among the tested anchors, protocatechuate groups were excellently performing the reaction, while vanillate and p-hydroxybenzoate led to minimal deposition of DHPs. Lignification behavior could be correlated with radical stability of phenolic anchor groups and the formation of benzodioxane structures of caffeate moieties. The presence of caffeate units that undergo trapping reaction, prevents cross-linking of cell wall components and enhances digestibility. Moreover, the benzodioxane motif increased rigidity and linearity of lignin, which is advantageous for material science applications, e.g. for bio-based carbon fibers.
木质素的化学难降解性限制了生物质的工业加工，所谓的设计型木质素可以解决这一问题。由单木质醇人工木质化形成的脱氢聚合物（DHP），能够独立于遗传信息进行结构-性能关系的研究。制备了纤维素酚酸酯薄膜，并将其用于带耗散监测的石英晶体微天平（QCM-D）实验，以实时研究表面聚合反应。酚类锚定基团显著影响木质化速度、沉积质量以及所得DHP层的刚性。通过HSQC核磁共振光谱对木质素结构中的连接类型进行了定量分析。聚合效率按阿魏酸＜对香豆酸＜咖啡酸的顺序增加。在所测试的锚定基团中，原儿茶酸基团的反应性能优异，而香草酸和对羟基苯甲酸导致DHP的沉积量最少。木质化行为与酚类锚定基团的自由基稳定性以及咖啡酸部分苯并二恶烷结构的形成相关。发生捕获反应的咖啡酸单元的存在可防止细胞壁成分交联并提高消化率。此外，苯并二恶烷基序增加了木质素的刚性和线性，这对于材料科学应用（例如用于生物基碳纤维）是有利 的。
