Low-Molecular-Weight Organo- and Hydrogelators Based on Cyclo(l-Lys-l-Glu)

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• 作者：Huimin Geng ; Lin Ye ; Ai-ying Zhang ; Jingbo Li ; Zeng-guo Feng
• 刊名：Langmuir
• 出版年：2016
• 出版时间：May 10, 2016
• 年：2016
• 卷：32
• 期：18
• 页码：4586-4594
• 全文大小：692K
• 年卷期：0
• ISSN：1520-5827

文摘

Four cyclo(l-Lys-l-Glu) derivatives (3–6) were synthesized from the coupling reaction of protecting l-lysine with l-glutamic acid followed by the cyclization, deprotection, and protection reactions. They can efficiently gelate a wide variety of organic solvents or water. Interestingly, a spontaneous chemical reaction proceeded in the organogel obtained from 3 in acetone exhibiting not only visual color alteration but also increasing mechanical strength with the progress of time due to the formation of Schiff base. Moreover, 6 bearing a carboxylic acid and Fmoc group displayed a robust hydrogelation capability in PBS solution. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the characteristic gelation morphologies of 3D fibrous network structures in the resulting organo- and hydrogels. FT-IR and fluorescence analyses indicated that the hydrogen bonding and π–π stacking play as major driving forces for the self-assembly of these cyclic dipeptides as low-molecular-weight gelators. X-ray diffraction (XRD) measurements and computer modeling provided information on the molecular packing model in the hydrogelation state of 6. A spontaneous chemical reaction proceeded in the organogel obtained from 3 in acetone exhibiting visual color alteration and increasing mechanical strength. 6 bearing an optimized balance of hydrophilicity to lipophilicity gave rise to a hydrogel in PBS with MGC at 1 mg/mL.