带极性侧链的环[6]芳酰胺的球形自组装

Spherical Assemblies of Cyclo[6]aramide with Polar Side Chains

环芳酰胺是一类基于三中心氢键促进,经寡聚前体一步大环合成法得到的刚性大环分子.通过紫外-可见(UV-Vis)光谱、动态光散射(DLS)、扫描电镜(SEM)、透射电镜(TEM)和原子力显微镜(AFM)等实验手段,详细考察了侧链为三甘醇单甲基醚链,由六个苯环单元组成的环[6]芳酰胺的自组装行为.实验结果表明,该大环在1,2-二氯乙烷中发生自组装,其组装聚集体随温度升高产生从聚集体到单分子的解聚变化,至70℃时几乎完全解聚;在由良溶剂(二氯甲烷)和不良溶剂(芳烃类)组成的混合溶剂中,带有三甘醇醚链的环[6]芳酰胺化合物1自组装成微球,结合热稳定性实验和TEM证实是实心微球而非囊泡.进一步发现微球形成和形貌依赖于混合溶剂中不良溶剂的极性和种类,芳烃类溶剂有利于微球形成,而烷烃和极性溶剂则不利,后者更倾向于形成膜的结构.

Cyclic aromatic oligoamides are a new class of recently discovered shape-persistent macrocycles.These molecules are prepared in high yields based on a one-step macrocyclization strategy that relies on hydrogen bond-enforced folding of the corresponding uncyclized oligomeric precursors.Macrocycle 1 is a member of a series of six-residue macrocycles dubbed cyclo[6]aramides and bears polar side chains derived from tri（ethylene glycol） monomethyl ether.We investigated its self-assembly using multiple techniques including UV-Vis spectrum,dynamic light-scattering（DLS）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and atomic force microscopy（AFM）.Results from these experiments demonstrated that 1 aggregates in apolar solvents such as 1,2-dichloroethane.As temperature increases,the supramolecular aggregates gradually disintegrate into molecularly dissolved species.For example,at 70 ℃,compound 1 exists mainly in its molecularly dissolved form.In mixed solvents consisting of good（dichloromethane） and poor（aromatic hydrocarbons） components,compound 1 aggregates into spherical assemblies.These self-assembling spheres were shown by studies on thermal stability and by TEM imaging to be solid balls instead of hollow vesicles.The formation of the microspheres was found to be dependent on the properties of the poor solvents as their formation was promoted in aromatic hydrocarbons and obliteratedin aliphatic and polar solvents.In aliphatic and polar solvents,macrocycle 1 was found to assemble into films.