Dissymmetric Triaryltriazines: Small Mass Columnar Glasses

• Published in: Chemistry : a European journal Vol. 29; no. 46; pp. e202301319 - n/a
• Main Authors: Nunes da Silva, Fabrícia, Marchi Luciano, Hugo, Stadtlober, Carlos H., Farias, Giliandro, Durola, Fabien, Eccher, Juliana, Bechtold, Ivan H., Bock, Harald, Gallardo, Hugo, Vieira, André A.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 15-08-2023; Wiley-VCH Verlag
• Subjects: Anisotropic fluids; Anisotropy; Annealing; Chemical Sciences; Chemistry; columnar liquid crystal; Crystallization; Crystals; cyclotrimerization; Emission spectra; Fluorescence; Liquid crystals; mesophases; molecular glass; Room temperature; Triazine; columnar liquid crystal; mesophases; molecular glass; cyclotrimerization; triazine
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202301319

Columnar liquid crystals with very small molecular masses that form anisotropic glasses well above room temperature are obtained by mixed dissymmetric substitution of sym‐triazine with ester‐bearing phenyl and phenanthryl or tetrahelicenyl moieties. The combination of low molecular symmetry with configurational flexibility and short polar ester moieties stabilizes the mesophase over large temperature ranges and induces pronounced calorimetric glass transitions within the anisotropic fluid despite the smallness of the molecules. In contrast to more symmetrical homologs, no ester tails longer than ethyl are necessary to induce the liquid crystalline state, allowing for the near‐absence of any insulating and weight‐increasing alkyl periphery. Films drop‐cast from solution show in all cases emission spectra that do not show significant change of fluorescence emission upon annealing, indicating that the columnar hexagonal mesoscopic order is obtained directly upon deposition from solution and is resistant to crystallization upon annealing.
Cotrimerization of complementary benzonitriles leads to dissymmetric triaryltriazines that form anisotropic mesomorphic luminescent glasses at very small molecular weight.