含N, N’-二苯吡啶醯胺凝膠分子其自組裝行為研究
Abstract
我們成功合成出一系列具有phenylethynylthiophene carboxamide為主體結構的有機凝膠化合物，M6、M12、M18以及Mchiral。其中凝膠分子M6、M12、M18、Mchiral在大部分的有機溶劑中皆可以形成凝膠，其形成凝膠主要是透過分子間的氫鍵、π-π堆疊作用力以及微弱的凡得瓦爾力，有序的自組裝排列成為螺旋結構，再進一步構築成三維的網狀結構，使得溶劑被包覆於其中，於是便形成凝膠。同時我們也觀察到凝膠分子結構上不同的長碳鏈，對於其凝膠分子形成凝膠的能力似乎有一定的影響。
透過TEM和AFM的觀察，M6、M12、M18以及Mchiral若在特定有機溶劑中，其凝膠分子會自組裝排列成一螺旋纖維結構，尤其是AFM我們甚至清楚的看見左旋(left-handed)和右旋(right-handed)的螺旋纖維結構交錯在其凝膠內部，也清楚觀察到其螺旋纖維彼此纏繞成更粗壯的螺旋結構。接著再藉由XRD實驗確認其螺旋排列主要是以分子間距離為半徑，做有規則的螺旋堆疊排列。透過模擬計算結果更是與我們實驗結果相當吻合。
最後在我們設計的有機凝膠系統裡，當我們在無光學活性的凝膠分子M6、M12、M18中添加少量具有光學活性的凝膠分子Mchiral，當分子開始自組裝排列時會受到Mchiral的調控，使得分子會重新排列成具有單一方向的螺旋結構，並同時透過CD光譜我們也的確觀察到M6、M12、M18 從無光學訊號轉變成具有很明顯的光學訊號，在我們設計的實驗裡，我們成功的引導出“sergeants and soldiers”效應。
A series of low molecular weight organogelators based on phenylene ethynylene carboxamide function groups, which can gel essentially all kinds of common organic solvents, was designed and synthesized. The formation of gel is attributed to self-assembly of individual molecules via cooperative hydrogen bonding and π-π stacking effect to form three-dimensional networks and subsequently immobilize the solvent molecules inside the networks via weak van der Waals interaction. We also observed that different chain length in the tails of the organogelators would influence gelation ability with different organic solvents. Surprisingly, M6, M12, M18 and Mchiral dissolved in some specific organic solvents were found to self-assemble into fibrous structures with helical arrangements where we could observe the left-handed and right-handed helices in the organogels, which were confirmed by AFM and TEM. XRD experiments revealed the relationship between the molecular frameworks and the dimension of the helical structures. Moreover, the molecular dynamics (MD) simulations further confirmed the experimental observations. Finally, the addition of chiral Mchiral molecules into the non-chiral M6, M12 and M18 aggregates results in the macroscopic chirality, which was confirmed by the appearance of the cotton effect in the CD spectra. The ability of Mchiral to induce the homochiralty of a bulk non-chiral aggregate based on the“sergeants and soldiers effect”signifies the importance of self-organization in the gel formation process
A series of low molecular weight organogelators based on phenylene ethynylene carboxamide function groups, which can gel essentially all kinds of common organic solvents, was designed and synthesized. The formation of gel is attributed to self-assembly of individual molecules via cooperative hydrogen bonding and π-π stacking effect to form three-dimensional networks and subsequently immobilize the solvent molecules inside the networks via weak van der Waals interaction. We also observed that different chain length in the tails of the organogelators would influence gelation ability with different organic solvents. Surprisingly, M6, M12, M18 and Mchiral dissolved in some specific organic solvents were found to self-assemble into fibrous structures with helical arrangements where we could observe the left-handed and right-handed helices in the organogels, which were confirmed by AFM and TEM. XRD experiments revealed the relationship between the molecular frameworks and the dimension of the helical structures. Moreover, the molecular dynamics (MD) simulations further confirmed the experimental observations. Finally, the addition of chiral Mchiral molecules into the non-chiral M6, M12 and M18 aggregates results in the macroscopic chirality, which was confirmed by the appearance of the cotton effect in the CD spectra. The ability of Mchiral to induce the homochiralty of a bulk non-chiral aggregate based on the“sergeants and soldiers effect”signifies the importance of self-organization in the gel formation process
Description
Keywords
膠體, 有機凝膠, gelator, organogel, sergeants and soldiers