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Melamine-barbiturate/cyanurate binary organogels possessing rigid azobenzene-tether moiety.

Research paper by Shiki S Yagai, Takashi T Karatsu, Akihide A Kitamura

Indexed on: 16 Nov '05Published on: 16 Nov '05Published in: Langmuir



Abstract

Binary organogels were prepared from coaggregates of azobenzene-tethered melamine dimer and cyanurate/barbiturates. In the gels of hydrocarbon liquids, the coaggregates formed heavily entangled nanofibers, morphologies of which are dramatically different from the previously reported coaggregates based on flexible dodecamethylene-tethered melamine dimers. In the present systems, the rigidity of the azobenzene tether may induce regular packing of molecules. In addition, UV-vis and IR spectroscopic measurements provided unequivocal evidence for the contribution of the central amide groups and the azobenzene chromophores in the tether moiety upon forming well-defined nanofibers by hydrogen-bonding and face-to-face (H-type) pi-pi stacking interactions, respectively. As a result of tight molecular packing in the self-assembled nanofibers, the azobenzene moiety in the gel state showed remarkable resistance to trans --> cis isomerization upon irradiation with UV light.