Lignin is the second most abundant naturally occurring biopolymer from lignocellulosic biomass. While there are several lignin applications, attempts to add value to lignin are hampered by its inherent complex and heterogenous chemical structure. This work assesses the organosolv lignin aggregates behaviour of soluble lignin extract derived from Miscanthus × giganteus using different ethanol concentrations (50%, 40%, 30%, 20%, 10% and 1%). The effect of two different lignin concentrations using similar ethanol concentration on the efficacy of esterification was studied. Overall, particle size of lignin analysis showed that the particle size of lignin aggregates decreased with lower ethanol concentrations. 50% ethanol concentration of soluble lignin extract showed the highest particle size of lignin (3001.8 nm), while 331.7 nm of lignin particle size was recorded at 1% ethanol concentration. Such findings of particle size correlated well with the morphology of the lignin macromolecules. The lignin aggregates appeared to be disaggregated from population of large aggregates to sub-population of small aggregates when the ethanol concentration was reduced. Light microscopy images analysis by ImageJ shows that the average diameter and circularity of the corresponding lignin macromolecules differs according to different ethanol concentrations. The dispersion of lignin aggregates at low ethanol concentration resulted in high availability of hydroxyl group in the soluble lignin extract. The efficacy of the lignin modification via esterification was evidenced directly via FTIR using the similar ethanol concentration of soluble lignin extract at different lignin concentrations. This study provided the understanding of detail analysis on particle size determination, microscopic properties and structural insights of lignin aggregates at wider ethanol concentrations. The esterified lignin derived at 5 mg/mL is suggested to expand greater lignin functionality in the preparation of lignin bio-based materials.

中文翻译：

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芒草可溶性木质素提取物在不同乙醇浓度下的有机溶剂木质素聚集行为及其对木质素酯化反应的影响

木质素是木质纤维素生物质中含量第二丰富的天然生物聚合物。虽然木质素有多种应用，但木质素固有的复杂和异质化学结构阻碍了为木质素增加价值的尝试。这项工作使用不同的乙醇浓度（50%、40%、30%、20%、10% 和 1%）评估了源自芒草 × giganteus 的可溶性木质素提取物的有机溶剂木质素聚集体行为。研究了使用相似乙醇浓度的两种不同木质素浓度对酯化功效的影响。总体而言，木质素粒度分析表明，木质素聚集体的粒度随着乙醇浓度的降低而减小。50% 乙醇浓度的可溶性木质素提取物表现出最高的木质素粒径 (3001.8 nm)，而 331. 在 1% 乙醇浓度下记录的木质素粒径为 7 nm。这种粒度的发现与木质素大分子的形态密切相关。当乙醇浓度降低时，木质素聚集体似乎从大聚集体的群体分解为小聚集体的亚群体。ImageJ 的光学显微镜图像分析表明，相应的木质素大分子的平均直径和圆形度根据乙醇浓度的不同而不同。木质素聚集体在低乙醇浓度下的分散导致可溶性木质素提取物中羟基的高可用性。使用相似乙醇浓度的可溶性木质素提取物在不同木质素浓度下通过 FTIR 直接证明了通过酯化进行木质素改性的功效。该研究提供了对更广泛乙醇浓度下木质素聚集体的粒度测定、微观特性和结构洞察的详细分析的理解。建议使用 5 mg/mL 的酯化木质素在木质素生物基材料的制备中扩展更大的木质素功能。