Solvent-Dependent Properties and Higher-Order Structures of Aryl Alcohol + Surfactant Molecular Gels

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• 作者：Shotaro Katsube ; Masaru Kinoshita ; Kenshi Amano ; Takaaki Sato ; Yukiteru Katsumoto ; Tatsuya Umecky ; Toshiyuki Takamuku ; Toshihiko Kaji ; Masahiro Hiramoto ; Yoko Tsurunaga ; Katsura Nishiyama
• 刊名：Langmuir
• 出版年：2016
• 出版时间：May 3, 2016
• 年：2016
• 卷：32
• 期：17
• 页码：4352-4360
• 全文大小：476K
• 年卷期：0
• ISSN：1520-5827

文摘

Molecular organogels, comprising small organic gelators in solvents, can be applied for dispersal of optical devices, such as emitters. Phenolic compounds and the surfactant bis(2-ethylhexyl) sulfosuccinate (AOT) are known examples of self-assembly organogels. However, conventional phenol + AOT gels in aromatic and acyclic alkane solvents are optically turbid, which is an obstacle for use as host materials in optical devices. In this study, a variety of aryl alcohol–AOT–solvent sets have been investigated systematically, and the correlation between the molecular architecture and optical transparency of the gels was considered. Accordingly, p-chlorophenol + AOT gels in cyclic alkane solvents were shown to form optically transparent gels. In contrast, aromatic and acyclic alkane solvents gave rise to turbid or opaque gels, even when utilizing the same gelators. AFM, NMR, SAXS, and FTIR were employed to determine the organogel structures. Consequently, we found that the gel transparency strongly depends on the size of the fibrous network of the gel, the structure of which is attributed to higher-order aggregates of the gelators. The average contour length and diameter of the fibrous network, l_av and d_av, respectively, were determined from AFM images. The transparent gels were shown to have l_av = 4–9 μm and d_av ≤ 0.3 μm, whereas the turbid gels had l_av = 15 μm and d_av = 0.4–0.6 μm. Such differences in the size of the fibrous network significantly affected the mechanical response of the gels, as shown by stress–strain measurements.