A lignin-based gel (AL-PE gel) was obtained from hardwood acetic acid lignin (AL) and poly(ethylene glycol) diglycidyl ether (PE) as a cross-linker at a high AL concentration, while the reaction at a lower AL concentration yielded an amphipathic derivative (am-AL-PE). The gel has been reported to swell in aqueous ethanol but shrink in pure water and ethanol. In the present work, swelling behaviors in other aqueous binary solvents and the swelling mechanism were investigated to explore novel lignin-based functional materials, such as stimuli-and/or environment-responsive gels. The AL-PE gel swelled in aqueous methanol, isopropanol, acetone, and tetrahydrofuran, and the order of swelling in the solvents was consistent with that of the am-AL-PE. Spin-spin relaxation time (T₂) measurements with ¹H NMR analysis of the gel in aqueous acetone revealed that gel swelling was closely related to an increasing T₂ of acetone bound to the gel network. The nature of the lignin moiety in the gel also enabled a pH response, and the amphipathic nature of the gel provided it with a function as an absorbent for cationic surfactants. The results of this study can contribute to the valorization of lignin as a main component for solvent sensors and environmental purification materials.

中文翻译：

---

响应于水性二元溶剂和pH值的木质素基凝胶的表征

木质素基凝胶（AL-PE凝胶）是在高AL浓度下从硬木乙酸木质素（AL）和聚（乙二醇）二缩水甘油醚（PE）作为交联剂获得的，而反应在较低AL下浓缩得到两亲衍生物（am-AL-PE）。据报道该凝胶在乙醇水溶液中溶胀，但在纯水和乙醇中收缩。在目前的工作中，研究了在其他水性二元溶剂中的溶胀行为和溶胀机理，以探索新型的木质素基功能材料，例如刺激和/或环境响应性凝胶。AL-PE凝胶在甲醇，异丙醇，丙酮和四氢呋喃水溶液中溶胀，在溶剂中的溶胀顺序与am-AL-PE一致。自旋-自旋弛豫时间（T ₂）测量在丙酮水溶液中的凝胶的¹ H NMR分析表明，凝胶溶胀与与凝胶网络结合的丙酮T ₂的增加密切相关。凝胶中木质素部分的性质还能够实现pH响应，并且凝胶的两亲性质使其具有充当阳离子表面活性剂的吸收剂的功能。这项研究的结果可以促进木质素的增值，木质素作为溶剂传感器和环境净化材料的主要成分。