Acid-Catalyzed Thermal Condensation Mechanism of the Dehydrogenation Polymer (DHP)

作者：Rui Luo, Xiong Wang, Kexin Li, Junqing Li, Junjun Chen, Junxian Xie, Rong Zhang, Peng Wang · 发表于：ACS Sustainable Chemistry & Engineering · 年份：2025 · DOI：10.1021/acssuschemeng.5c04738 · 被引用次数：2 · 研究领域：Lignin and Wood Chemistry、Polymer composites and self-healing、Carbon dioxide utilization in catalysis

Milled wood lignin, also known as native lignin, exhibits an outstanding adhesive performance in wood-bonding applications. However, the thermal condensation mechanism remains unclear. In this study, we synthesized dehydrogenation polymer (DHP) with structural similarity to native lignin and used 13 C isotopic labeling coupled with NMR spectroscopy to elucidate the thermal condensation mechanism under hot-pressing conditions. The α, β, and γ positions of the side chain in the coniferin were selectively 13 C labeled and that via enzyme catalysis to prepare DHP-[α- 13 C], DHP-[β- 13 C], and DHP-[γ- 13 C], respectively. 13 C isotope tracing confirmed that the main active site for DHP thermal condensation was C γ in the side chain of the coniferyl alcohol structure. The underlying mechanism possibly involves acetic-acid-mediated protonation of the hydroxyl group, generating a resonance-stabilized allylic carbocation that undergoes electrophilic aromatic substitution at the electron-dense C 6 position of the aromatic ring. Our work provides valuable insights into the molecular mechanism underlying lignin thermal condensation, facilitating the development of biobased adhesives.