木质素由于其复杂和部分疏水的结构而被忽略并长期用作废物。已经进行了许多努力来克服这些缺陷,并将其用作高价值产品,不足以在各种先进应用中充分发挥木质素的潜力,因为它们需要获得更具体和微调的化学结构的程序。这项工作的重点是获得来自牛皮纸和有机溶剂分离过程的不同结构的亲水性木质素。研究了不同类型木质素的化学结构,并分析了改性过程中结构差异及其后续性能的影响,为各种目的提高其潜在应用价值。进行羧甲基化和磺甲基化反应的目的是增强木质素样品的极性,而甲基化反应旨在获得稳定性较高的木质素。样品的物理化学分析,由FTIR进行,GPC,31PNMR,13CNMR,和HSQCNMR,验证了所选择的化学反应和条件的有效性,获得具有较低羟基含量的木质素,由于它们取代和插入羧基甲基,磺甲基和甲基,因此获得更多的浓缩,芳香和含氧芳香碳结构。虽然甲基化反应在取代OH基团方面最有效,由于其非选择性,OL显示出比KL更高的改性产率。在热和形态特性方面,分别通过DLS和TGA进行分析,观察到改性样品显示较低的Z电位值,随着更高的电导率,作为磺甲基化的有机溶剂木质素,显示出最好的结果,这也是具有最小粒度和多分散指数的一种。最后,所有修改的样品都显示出更高的T50%值,表明对降解有更好的稳定性。
Lignin has been overlooked and used as a waste for long due to its complex and partially hydrophobic structure. Many efforts have been carried out to overcome these deficiencies and apply it as a high-value product, which are insufficient to reach the full potential of lignin in various advanced applications, since they require with procedures for the obtaining of more specific and fine-tuned chemical structures. This work focuses on the obtaining of differently structured hydrophilic lignins derived both from Kraft and organosolv isolation processes. The chemical structures of the different lignin types were studied, and the effect of the structural differences in the modification processes and their subsequent properties analyzed, valorizing their potential application for diverse purposes. The carboxymethylation and sulfomethylation reactions were carried out with the aim of enhancing the polarity of the lignin samples, while the methylation reaction aimed to obtain lignins with higher stability. The physicochemical analyses of the samples, carried out by FTIR, GPC, 31P NMR, 13C NMR, and HSQC NMR, verified the effectiveness of the chemical reactions and conditions selected, obtaining lignins with lower hydroxyl content, due to their substitution and insertion of carboxymetyl, sulfomethyl and methyl groups, therefore obtaining more condensed, aromatic and oxygenated aromatic carbon structures. While the methylation reaction was the most efficient in substituting the OH groups, due to its non-selectivity, OL showed higher modification yields than KL. In terms of the thermal and morphological properties, analyzed by DLS and TGA respectively, it was observed that the modified samples showed lower Z potential values, along with higher conductivity, being the sulfomethylated organosolv lignin the one showing the best results, which was also the one with the smallest particle size and polydispersity index. Finally, all the modified samples showed higher T50% values, suggesting a better stability towards degradation.