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Issue 19, 2011
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Solvent effects on structure, photoresponse and speed of gelation of a dicholesterol-linked azobenzene organogel

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Abstract

By introducing methanol as a co-solvent into cyclopentanone, solvent effects on structure, photoresponse and speed of gelation of a dicholesterol-linked azobenzene organogel DCAZO2 have been investigated. Optical microscopy (OM) and scanning electron microscopy (SEM) images reveal that the gel fibers form macroscopic aggregates by adding methanol. Minimum gelation concentration (MGC) of the gels decreases with increasing methanol content, while the gel-to-sol transition temperature (Tgel) decreases firstly and increases afterwards. For photoisomerization (corresponding to gel-sol transition), the first stage rate constant kg1 of the gels decreases with increasing methanol content. The photoisomerization process of the gel with 5% methanol is different from the other five samples, whose first stage rate constant kg1 is greater than its second stage rate constant kg2. By increasing methanol content from 0% to 30%, gelation time (corresponding to sol–gel transition) of both heated gel and UV-visible light irradiated gel decreases from 7 h to 5 min and 6 h to 0 min (before visible light irradiation is accomplished), respectively. Solubility parameters and Teas plots of the gelator and mixed solvents are systematically calculated to estimate the gelator-solvent interaction. It is found that gelation requires that the gelator-solvent interaction be neither too strong nor too weak, otherwise solution or precipitate are formed.

Graphical abstract: Solvent effects on structure, photoresponse and speed of gelation of a dicholesterol-linked azobenzene organogel

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Publication details

The article was received on 01 Jul 2011, accepted on 08 Jul 2011 and first published on 17 Aug 2011


Article type: Paper
DOI: 10.1039/C1SM06240A
Citation: Soft Matter, 2011,7, 9177-9183
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    Solvent effects on structure, photoresponse and speed of gelation of a dicholesterol-linked azobenzene organogel

    Y. Wu, S. Wu, G. Zou and Q. Zhang, Soft Matter, 2011, 7, 9177
    DOI: 10.1039/C1SM06240A

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