The mechanisms behind lignin dissolution with protic ionic liquids (PILs) and their influence over lignin properties remain not fully explored. In this work, physicochemical and structural features of lignins extracted from sugarcane bagasse after pretreatment with a series of PILs (length of the cation chain combined with different anions) were assessed using analytical techniques. It was found that the lignin extracted with shorter chain length cations PILs showed the highest β-O-4 content. Opposite, the increase of the PILs cation chain length resulted in enhanced depolymerization. All lignins presented high polydispersity (>3.7), while the weight average molecular ranged from 1921 to 13,539 g/mol. The recovered [Eti][Mal] lignin presented the higher β-O-4 content and was possibly the most preserved lignin obtained. Opposite, lignin isolated from [Hex][Ac] and [Hex][For] treatments had less β-O-4 linkages attributed to the depolymerization of lignin via rupture of ether linkages generating intermediates that further repolymerized and/or depolymerized. These results suggest that the ionicity of the PIL is a crucial factor for lignin dissolution. Furthermore, these results illustrate that the proposed pretreatment using different PILs is useful to obtain high-quality lignins with distinct features and opens a new perspective for materials to match various applications.

木质素被质子离子液体（PIL）溶解的机理及其对木质素性能的影响仍未得到充分探讨。在这项工作中，使用分析技术评估了用一系列PIL预处理后从甘蔗渣中提取的木质素的理化和结构特征（阳离子链的长度与不同的阴离子结合）。发现用较短链长阳离子PILs提取的木质素显示出最高的β-O-4含量。相反，PILs阳离子链长度的增加导致解聚作用增强。所有木质素均表现出高多分散性（> 3.7），而重均分子的范围为1921至13,539 g / mol。回收的[Et] [Mal]木质素具有较高的β-O-4含量，可能是获得最多的木质素。对面，通过醚键的断裂产生中间体，该中间体进一步再聚合和/或解聚。这些结果表明，PIL的离子性是木质素溶解的关键因素。此外，这些结果表明，所建议的使用不同PIL的预处理对于获得具有独特特征的高质量木质素很有用，并为适应各种应用的材料开辟了新的前景。