為了探討含不同烷基鏈段對於自組裝系統的影響，本研究致力於含不同烷基鏈段膽固醇光敏性有機凝膠體之合成與光學特性探討，分別為：Cholesteryl (4-nitro-azobenzene-4′-oxy) carbonate (NA0)、Cholesteryl 3-(4-nitro-azobenzene-4′-oxy) propyl carbonate (NA3)、Cholesteryl 6-(4-nitro-azobenzene-4′-oxy) hexyl carbonate (NA6)、Cholesteryl 11-(4-nitro-azobenzene-4′-oxy) undecyl carbonate (NA11)。經凝膠化能力測試後發現，除了 NA11 外皆具有凝膠化的能力，而且以 NA0 的凝膠化能力為最佳。結果顯示，雖然長碳鏈段可增加凡德瓦力，但在此系統中，則容易造成析出而不利於膠體化。為了探討超分子凝膠的微結構，使用 SEM、 TEM 進行觀察，發現到分子可自組裝成螺旋狀的纖維結構，並且可進一步交聯成三維的網狀結構，而形成超分子凝膠。本研究所合成的化合物因為具有偶氮苯基團，理論上，可利用紫外光與可見光來進行溶液態與凝膠態的調控，結果發現只有在非極性溶液下所形成的凝膠可利用紫外光與可見光進行溶液態與凝膠態轉換。結果顯示，在極性溶液下與非極性溶液下，分子存在著不同的自組裝排列，並以 1H-NMR、 FTIR、 UV-Vis spectra 證明。此外，為了探討分子的液晶特性，也利用了 DSC 與 POM 來進行量測。最後將這些具有光學活性的化合物與市售液晶 HSG 22200 進行摻混而配置成液晶物理複合材料，觀察其液晶相的變化。

To investigate the effect of alkyl chain length on the self-assembly of molecules, a series of cholesteric photosensitive organogelators consisting of Cholesteryl (4-nitro-azobenzene-4′-oxy) carbonate (NA0), Cholesteryl 3-(4-nitro-azobenzene-4′-oxy) propyl carbonate (NA3), Cholesteryl 6-(4-nitro-azobenzene-4′-oxy) hexyl carbonate (NA6), and Cholesteryl 11-(4-nitro-azobenzene-4′-oxy) undecyl carbonate (NA11) were synthesized. From the results of gelation in various solvents, it was found that all NA derivatives reveal gelation behavior, except NA11. The results suggest that longer alkyl chain length may increase van Der Waals force, however, simultaneously decrease the formation of self-assembled gels. In addition, SEM and TEM were used to study the micro structure of the self-assembled constructions. Some helical structures via supramolecular assembly and three dimensional networks were observed. The synthesized NA derivatives contain a photosensitive azobenzene group. Theoretically, a stimuli induced reversible gel-solution transition should be observed. Surprisingly, the UV-vis induced reversible gel-solution transition can only be seen in nonpolar solvents. In polar solvents, no any reversible transition is seen. The results are ascribed to the different assembly of molecules in the two systems. The results were confirmed using 1H-NMR、FTIR、and UV-Vis analysis. Furthermore, liquid crystalline properties of the synthesized NA molecules were investigated using DSC and POM. Optical properties and variation of cholesteric textures of liquid crystalline composites via mixing commercially available HSG22200 Nematic liquid crystal with the synthesized chiral NA derivatives were studied.

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