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Issue 2, 2011
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Photoinduced reversible gel–sol transitions of dicholesterol-linked azobenzene derivatives through breaking and reforming of van der Waals interactions

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Abstract

A series of new symmetric dicholesterol-linked azobenzene gelators with different spacer lengths have been synthesized. The compounds with spacers of zero, two or six methylene units are denoted as DCAZO0, DCAZO2 and DCAZO6, respectively. A gelation test reveals that a subtle change in the length of the spacer can produce a dramatic change in the gelation behavior of the compounds. DCAZO2 obtains the minimum gelation concentration among the three gelators. For cyclopentanone gel of DCAZO2, the reversible gel–sol transitions by irradiation with UV and visible light are investigated by UV-vis absorption and circular dichroism (CD) spectra, SEM, TEM and XRD analyses. Upon UV irradiation of the gel, transcisphotoisomerization of the azobenzene groups occurs, the change in molecular polarity leads to the breaking of van der Waals interactions, resulting in the gel–sol transition. The gel can be recovered by the reverse cistransphotoisomerization after the exposure to visible light. SEM, TEM and XRD studies reveal that the gelator molecules self-assemble into one-dimensional fibers with diameters 50–100 nm in an anticlockwise direction, which further crossed-linked to form three-dimensional networks.

Graphical abstract: Photoinduced reversible gel–sol transitions of dicholesterol-linked azobenzene derivatives through breaking and reforming of van der Waals interactions

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Publication details

The article was received on 05 May 2010, accepted on 27 Sep 2010 and first published on 08 Nov 2010


Article type: Paper
DOI: 10.1039/C0SM00330A
Citation: Soft Matter, 2011,7, 716-721
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    Photoinduced reversible gel–sol transitions of dicholesterol-linked azobenzene derivatives through breaking and reforming of van der Waals interactions

    Y. Wu, S. Wu, X. Tian, X. Wang, W. Wu, G. Zou and Q. Zhang, Soft Matter, 2011, 7, 716
    DOI: 10.1039/C0SM00330A

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