Two's complement: A series of discotic hydrogen‐bonded complexes was prepared from a “clicked” triazole derivative with C3 symmetry and carboxylic acids (see picture; R1, R2=alkyl groups). Owing to the extended rigid core structure, the supramolecular discs could be stacked on top of each other, leading to hexagonal columnar liquid‐crystalline phases.
We prepared a series of C 3 -symmetry discogens with three 1,2,3-triazoles and a central benzene ring by a copper-catalyzed ''click reaction'' between 1,3,5-triethynylbenzene and 3,4,5-trialkoxybenzyl azides. According to the differential scanning calorimetry (DSC) data, compounds with octyl and dodecyl peripheries showed stable liquid crystalline (LC) phases at room temperature, and upon heating underwent an isotropization at 105.3 C and 92.2 C, respectively. Compound with octadecyl peripheries melted into a LC phase at 63.5 C, and changed into a disordered liquid at 84.4 C. As characterized by optical polarized microscopy (POM) and X-ray scattering techniques, all LC phases revealed hexagonally packed columns, the axes of which are aligned vertically on the glass substrate. Interestingly, the experimentally accessible crystalline phase of the compound with octadecyl chains kept the 2-D hexagonal columnar structure, although the interdisc distance within the columns changed at the transition from the LC to crystalline phase.
We synthesized three dendron-coil-dendron block copolymers consisting of ionophilic poly(ethylene oxide) (PEO) coils and mesogenic dendrons with four octadecyl peripheries via stepwise click reactions.The obtained polymers were doped with lithium triflate, whose concentration per ethylene oxide unit was 0.05. As characterized by optical polarized microscopy (POM) and X-ray scattering techniques, polymer 1 with the shortest PEO coil (M n ¼ 2000 g mol À1 ) did not show the liquid crystalline (LC) phase, while its ionic sample (1-Li + ) exhibited a hexagonal columnar LC phase. On the other hand, 2 and 3 (with PEOs of M n ¼ 4000 and 8000 g mol À1 , respectively) displayed identical LC morphologies to 2-Li + and 3-Li + , respectively, although the phase transition temperatures increased upon salt doping.For 2 and 2-Li + , gyroid and lamellar LC phases were observed with increasing temperature, while 3 and 3-Li + showed only a lamellar LC phase. The observed ion-transporting behavior was strongly dependent upon the connectivity of ion-conducting domain structures. The investigation of the morphology-conductivity correlation using a normalized conductivity (s* ¼ s/f, where s and f are the original conductivity and the PEO volume fraction) indicated that the 3-D gyroid LC phase showed the highest value, while the lowest conductivity was found in the 1-D columnar structure at identical temperatures. Additionally, the gyroid to lamellar phase transition temperature of 2-Li + could be determined by the s*, which was consistent with the X-ray data. Consequently, the results can be explained by the fact that the ionic pathway becomes complicated when going from higher to lower dimensional structures in polygrain samples.
Perfekt ergänzt: Eine Reihe discotischer H‐Brücken‐gebundener Komplexe wurde aus einem durch Klick‐Chemie hergestellten Triazolderivat mit C3‐Symmetrie und Carbonsäuren erhalten (siehe Bild; R1, R2=Alkylgruppen). Wegen ihrer ausgedehnten starren Kernstruktur konnten die supramolekularen Scheiben unter Bildung hexagonaler columnarer flüssigkristalliner Phasen aufeinander gestapelt werden.
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