小分子凝膠的形成，來自於分子間的自組裝機制，為了解分子結構對凝膠的生成和自組裝的影響，本研究設計兩組具螢光性質的化合物PA和DPA，分別為單邊含芘基的不對稱型分子，以及雙邊含芘基的對稱型分子。藉由改變結構中碳氫鏈基團的長度，探討碳鏈長度對凝膠化能力的影響。並藉由導入的芘螢光基團，探討在不同溫度下，凝膠態和溶液態對螢光強度和發光波長的影響，進一步透過螢光變化的趨勢，了解分子自組裝的堆疊結構。研究結果顯示，較長的碳氫鏈有利於分子在有機溶劑環境下形成凝膠態，且有助於提高凝膠的溶解溫度；結構對稱的分子DPA，除了分子間的作用力外，可透過分子摺疊的方式形成分子內的作用力，有助於提高凝膠的耐熱性，但於多數溶劑中不易形成凝膠。以TEM、SEM和變溫1H-NMR分析，分子間氫鍵作用力、π-π堆疊和凡德瓦爾力確實參與自組裝的過程，透過分子的堆疊排列，進一步形成三維網狀結構的超分子凝膠。利用螢光光譜在凝膠相轉換前、後隨溫度的變化，配合XRD測得的分子排列間距，我們針對兩種分子構型模擬出，在凝膠態時，PA17和DPA10分別是以螺旋和bi-layer的方式堆疊。

By controlling the length of alkyl chain, we have successfully synthesized a series of fluorescent low-molecular-weight gelators (LMWGs) of N-(pyrene-1-yl)alkyleneamide (PA) and N-(pyrene-1-yl)- N-(pyren-3-yl)alkylenedipamide (DPA) based on pyrene groups and amide moieties. Dependence of gelation properties on molecular chain length was studied. In addition, effect of pyrene group on fluorescence at different temperature under both liquid and gel states were investigated. The results show that the symmetric DPA reveals higher thermo stability but weaker gelation behavior as compared with asymmetric PA. From the results of SEM and TEM analysis, self-assembly of LMWGs forms nan-fiber and then 3D network constructions. Interestingly, both left-handed and right handed helical structures were observed under TEM. Theoretically, both racemic structures should be induced under achiral environment. From the results of temperature dependent 1H-NMR, a reasonable molecular arrangement of the self-assembled constructions via secondary forces were proposed. Furthermore, from the results of fluorescence spectra, the pyrene group of PA17 was found to change from monomer to excimer before and after gelation under UV-exposure. Oppositely, for symmetric compound DPA10, the pyrene group shows excimer behavior either in gel state or solution state. From the results of XRD and molecular simulation, both reasonable helical structure and bi-layer self-assembled model for PA17 and DPA10 were proposed.

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