Center for Advanced Materials, Forestry and Forest Products Research Institute (FFPRI), 1 Matsunosato, Tsukuba 305-8687, Japan.
Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
Molecules. 2023 Feb 5;28(4):1542. doi: 10.3390/molecules28041542.
Recently, a large-scale production system of softwood-derived poly(ethylene glycol) (PEG)-modified glycol lignin (GL) was developed to produce high-quality lignin derivatives with substantially controlled chemical structures and attractive thermal properties. In this study, the further upgrading of GL properties with carboxy functionalization was demonstrated through the room-temperature hydrogen peroxide (HO) treatment with the mass ratio of HO to GL, 1:1 and 1:3, for 7 d. The changes in the chemical structure, carboxy group content, molecular weight, and thermal properties of the insoluble portions of partially oxidized glycol lignins (OGLs) were then investigated. Nuclear magnetic resonance and thioacidolysis data revealed that the oxidative functionalization involved the cleavage of --4 linkages and the oxidative cleavage of guaiacyl aromatic rings into muconic acid-type structures. This was validated by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and potentiometric titration. Overall, the results suggested that the varying outcomes of carboxy group content (0.81-2.04 mmol/g OGL) after 7-d treatment depended on the type of the GL origin having varying amounts of the retained native lignin structure (e.g., --4 linkages), which were prepared from different source-wood-meal sizes and PEG molecular masses.
最近，开发了一种大规模的软木衍生聚乙二醇（PEG）修饰的二醇木质素（GL）生产系统，以生产具有受控化学结构和有吸引力的热性能的高质量木质素衍生物。在这项研究中，通过室温过氧化氢（HO）处理，进一步将 GL 的性能通过羧基官能化进行升级，HO 与 GL 的质量比为 1:1 和 1:3，处理时间为 7 天。然后研究了部分氧化二醇木质素（OGL）不溶性部分的化学结构、羧基含量、分子量和热性能的变化。核磁共振和硫代酸解数据表明，氧化官能化涉及--4 键的断裂和愈创木基芳环氧化断裂成富马酸型结构。这通过衰减全反射傅里叶变换红外（ATR-FTIR）光谱和电位滴定得到验证。总的来说，结果表明，7 天处理后羧基含量（0.81-2.04mmol/g OGL）的变化结果取决于 GL 来源的类型，其具有不同数量的保留的天然木质素结构（例如，--4 键），这些木质素是由不同来源木屑大小和 PEG 分子量制备的。
