【作者】 缪锴； 胡懿； 查宝； 许莉； 苗新蕊； 邓文礼；

【Author】 Kai Miao;Yi Hu;Bao Zha;Li Xu;Xinrui Miao;Wenli Deng;South China University of Technology;

【机构】 华南理工大学；

【摘要】 利用扫描隧道显微镜(S TM)研究了羟基和羰基官能团对于芴酮衍生物在不同溶剂(辛苯和辛酸)和不同浓度下的自组装结构的影响。实验结果表明,在羟基修饰的芴酮衍生物的二维自组装单分子层内,通过调控溶质浓度,在辛酸–石墨界面上依次形成了二聚体、交替结构、四聚体、八聚体、错排二聚体和线型条陇状六种不同的自组装结构。而在辛苯–石墨界面上,除了形成八聚体、错排二聚体和线型条陇状之外,还形成了一种新的随机排列的无序结构。而羧基修饰的芴酮衍生物则在固–液界面仅形成了两种自组装结构。结合计算表明,增强的分子间氢键作用是限制芴酮衍生物在固–液界面二维自组装结构单一的重要原因。此外,分子–分子间氢键、分子–溶剂间氢键以及分子间的范德华力作用等几种作用的相互竞争和协作是诱导羟基修饰芴酮衍生物形成多晶形的原因。而溶剂的性质(溶解度、氢键成键)会直接影响芴酮衍生物在低浓度下的二维自组装结构。更多还原

【Abstract】 The self-assembled behaviors of two fluorenone derivatives, 2, 7-bis((11-hydroxyundecyl)oxy)-9-fluorenone(BHUF) and 2, 7-bis((10-carboxydecyl)oxy)-9-fluorenone(BCDF), were investigated at the liquid–solid interface by scanning tunneling microscopy. Two solvents, 1-octanoic acid and 1-phenyloctane, were employed in consideration of their distinct polarity and solubility. It is observed that the BHUF molecules self-assemble into seven different polymorphs upon adsorption, while only two different polymorphs are observed in the BCDF monolayer. The theoretical calculation is performed to reveal the underlying mechanism. As compared to that of –C=O…HO– hydrogen bonds, the enhanced binding energy of intermolecular –C=O…HOOC– hydrogen bonds in the BCDF monolayer would dominate the intermolecular van der Waals(vd Ws) interactions and the molecule–solvent interactions, thereby resulting in a limitation of expression of structural polymorphism. In addition, the concentration-dependent polymorphism as well as the relative phase transition is discussed in terms of the stability and packing density of different polymorphs. Furthermore, the different self-assembled behaviors of BHUF molecules in these two solvents at lower concentrations are associated with the different energy gain upon solvent co-adsorption. The investigation provides a simple and alternative strategy to construct the structural polymorphs by utilizing multiple hydrogen bonds at the liquid–solid interface.更多还原