以谷氨酸二乙酯为头基的Bola型两亲分子在气液界面的组装：手性相互作用与膜结构

Interfacial Assembly of Diethyl Ester Glutamic Acid Terminated Bolaamphiphile at the Air/Water Interface:Chiral Interaction and Morphology

研究了双头基两亲分子(Bolaamphiphile)N,N′-1,14-十四烷二酸酰-L-谷氨酸二乙酯(L-HDGE)和它的对映异构体D-HDGE在气液界面的组装;考察了HDGE分子的界面组装结构以及头部基团的手性,膜压和离子液体亚相对组装结构的影响.采用原子力显微镜(AFM)和傅里叶变换红外(FTIR)光谱对组装体的微观结构和组装机理进行了研究.结果表明,HDGE(L-HDGE或D-HDGE)在水亚相上可以组装得到平行排列,宽为50-120nm,高为1-5nm的纳米线.而将L-HDGE与D-HDGE混合组装时,只会得到疏松的薄膜结构.红外光谱表明HDGE分子的异手性相互作用强于同手性作用.在表面压继续上升时,纳米线可以发生一定聚集生成纳米带.亚相为一定浓度的离子液体时,会促进分子的聚集,在膜压的共同影响下,纳米带可以卷曲形成螺旋结构,螺旋的方向取决于头基的分子手性.

We investigated the self-assembly behavior of bolaamphiphilic tetraethyl ester-di-L-glutamic acid-N,N′-hexadecanedioic amide （L-HDGE） and its enantiomer D-HDGE at the air/water interface.The self-assembled structures of the HDGE （L-HDGE or D-HDGE） molecule at the air/water interface and some other factors that affect the assembled structures, such as the chirality of the hydrophilic head group, surface tension, and ionic liquid subphase were studied.Atomic force microscopy （AFM） and Fourier transform infrared （FTIR） spectroscopy were employed to investigate the morphology and assembly mechanism of the transferred film.The HDGE molecule was found to form parallel nanowires on the surface of water with widths from 50 to 120 nm and heights from 1 to 5 nm while only a thin film was obtained when the racemic mixture was used under the same conditions.The FTIR spectra show that the heterochiral interaction of the HDGE molecule is stronger than the homochiral interaction.With an increase in surface tension, the parallel nanowires aggregate.Trace amounts of ionic liquid added to the subphase remarkably accelerated the aggregation of the nanowires to yield nanostrips, and some helical structures were observed when the surface tension was increased.The handedness of the helical structures was determined by the molecular chirality of the head group.