The direct use of lignin results in the synthesis and production of low-value materials. Therefore, the chemical modification of lignin increases not only its reactivity, but also improves its compatibility and better dispersion in the lignin-based polymeric materials where lignin acts as a good substitute for oil-based polyols. Systematic studies were conducted in the present work. Hydroxymethylated lignin (HML) was synthesized via its reaction with formaldehyde, and functional groups present in the sol fraction of HML were then quantitatively investigated by aqueous potentiometric/conductometry titration prior to any further modification and by 1 HNMR and FTIR techniques after reacting with α-bromoisobutyryl bromide, resulting in brominated HML (BHML). To calculate moles of hydroxyl groups per gram of HML, 1 HNMR of BHML was recorded in the presence of a given amount of N,N-dimethylformamide as an internal standard. It was found that the number of hydroxyl groups increases from 6.44 mmol/g in the lignin to 7.77 mmol/g in the HML. The moles of phenolic hydroxyl and carboxyl groups per gram of HML were calculated using aqueous titration. It was found that the moles of phenolic hydroxyl groups in the HML decrease by 19.8% compared to lignin. Due to poor solubility of the HML in tetrahydrofuran, BHML was used in the GPC analysis, from which the number average molecular weight ( $$\bar{M}_{\rm{n}}$$ M ¯ n ) of the HML was obtained after some calculations to be 1014 g/mol. It was observed that modification of lignin with formaldehyde increases not only its functional groups but also increases its molecular weight by creating methylene bridges between the two lignin molecules.

中文翻译：

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羟甲基化和 α-溴异丁酰化是表征羟甲基化木质素官能团的有效而精确的方法

木质素的直接使用导致低价值材料的合成和生产。因此，木质素的化学改性不仅提高了其反应性，而且提高了其在木质素基聚合物材料中的相容性和更好的分散性，其中木质素作为油基多元醇的良好替代品。在目前的工作中进行了系统的研究。羟甲基化木质素 (HML) 是通过与甲醛反应合成的，HML 溶胶部分中存在的官能团在进一步修饰之前通过水电位/电导滴定进行定量研究，并在与 α-反应后通过 1 HNMR 和 FTIR 技术进行定量研究。溴化异丁酰溴，产生溴化 HML (BHML)。要计算每克 HML 的羟基摩尔数，BHML 的 1 HNMR 在存在作为内标的给定量 N,N-二甲基甲酰胺的情况下记录。发现羟基的数量从木质素中的 6.44 mmol/g 增加到 HML 中的 7.77 mmol/g。使用水滴定法计算每克 HML 的酚羟基和羧基的摩尔数。发现与木质素相比，HML 中酚羟基的摩尔数减少了 19.8%。由于 HML 在四氢呋喃中的溶解度较差，GPC 分析中使用 BHML，从中得出 HML 的数均分子量 ( $$\bar{M}_{\rm{n}}$$ M¯ n )经过一些计算得到 1014 g/mol。