Two cholesterol groups were for the first time attached to a lignin-derived metabolic intermediate, 2-pyrone-4,6-dicarboxylic acid (PDC). This PDC molecule showed a liquid crystalline mesophase and interesting organogelation behavior. The relationship between molecular structure and assembly properties was investigated by modifying the PDC core and a spacer group between the PDC and cholesterol moieties. Although all derivatives displayed similar phase transition behavior with a SmA phase, only a few of them could form organogels. Detailed morphology investigations of the xerogels by X-ray diffraction (XRD) and scanning electron microscopy (SEM) suggested that both the PDC moiety and a carbamate spacer are essential for the occurrence of organogelation. Hydrogen bonds of the carbamate spacers and van der Waals interactions of the cholesterol moieties lead to a dipolar-induced interaction of the pyrone rings. The physical gels were probably stabilized by these cooperative interactions. The IR and 1H NMR spectroscopies clearly revealed the presence of weak intermolecular interactions, such as hydrogen bonds and dipolar-type interactions, for efficient gelator molecules.
在木质素衍生的代谢中间体 2-吡喃酮-4,6-二羧酸(PDC)上首次连接了两个胆固醇基团。这种 PDC 分子显示出液晶介相和有趣的有机凝胶行为。通过改变 PDC 核心和 PDC 与胆固醇分子之间的间隔基团,研究了分子结构与组装特性之间的关系。尽管所有衍生物都显示出与 SmA 相类似的相变行为,但只有少数衍生物能形成有机凝胶。通过 X 射线衍射(XRD)和扫描电子显微镜(SEM)对这些异构凝胶进行的详细形貌研究表明,PDC 分子和氨基甲酸酯间隔基对发生有机凝胶化至关重要。氨基甲酸酯间隔物的氢键和胆固醇分子的范德华相互作用导致了吡喃酮环的双极性相互作用。物理凝胶可能是通过这些协同作用稳定下来的。红外光谱和 1H NMR 光谱清楚地揭示了高效凝胶剂分子中存在着微弱的分子间相互作用,如氢键和双极型相互作用。