| Abstract
| - Polycatenar-type organogelators, comprising a cyanochalcone unit and a half disklike phenyl group with two or three long alkoxy chains, formed stable organogels. The gelators were assembled into a head-to-tail type dimer by a dipole−dipole interaction between the polar head groups and further organized into columnar or layer structures through a π−π interaction. Upon photoirradiation in the gel state, the [2 + 2] addition reaction of the chalcone units occurred, which induced a gel-to-sol transition.
- We synthesized a series of compounds belonging to a new class of polycatenar-type organogelators,comprising a cyanochalcone unit and a half disklike phenyl group with two or three long alkoxy chains,and investigated their supramolecular assembly with respect to their molecular structures. They formedvery stable organogels in n-alkanes, cyclohexane, and alcohols. In the absence of a cyano group, thecompound did not show any gelation ability. Dry gels were prepared by freeze-drying the organogelsfrom hexane, and their structures were investigated by SEM and XRD. The SEM images of the dry gelsshowed the presence of elongated fibers, which formed a gel network. The dry gels exhibited differentpacking arrangements, depending on the volume fraction of the flexible tails in the gelator. The gelatorswere assembled into a head-to-tail type dimer by a dipole−dipole interaction between the polar headgroups and further organized into columnar or layer structures through a π−π interaction. The gelatorswith three alkoxy tails formed hexagonal, square, and rectangular columnar structures, depending on thetail length, while the gelator with two alkoxy tails formed a layer structure. The organogels werephotoresponsive. Upon photoirradiation, the [2 + 2] addition reaction of the chalcone units occurred,which induced a gel-to-sol transition.
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