Stable, Low-Temperature Discotic Nematic Superstructures by Incorporating a Laterally Substituted Sidearm in Hexakis(phenylethynyl)benzene Discogens

• Published in: Advanced functional materials 2007-08, Vol.17 (12), p.1896-1902
• Main Authors: Chien, S.-C., Chen, H.-H., Chen, H.-C., Yang, Y.-L., Hsu, H.-F., Shih, T.-L., Lee, J.-J.
• Format: Article
• Language: English
• Subjects: discotic; Liquid crystals; Liquid crystals, discotic, nematic; Mesogens; nematic; Structure-property relationships; Supramolecular materials
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200601019

A new strategy for preparing room‐temperature discotic nematic materials is proposed and developed stepwise to improve various discotic nematic properties. This approach replaces one sidearm of the discotic hexakis(4‐hexyloxyphenylethynyl)benzene with a tris(alkoxy) sidearm, 1‐ethynyl‐2,3,4‐tris(hexyloxybenzene), to lower transition temperatures, manipulate discotic nematic ranges, and preserve the discotic nematic superstructure while preventing column formation. Although symmetry considerations play a role in the resulting mesogenic properties, steric hindrance and van der Waals interactions are ascribed to the superior discotic nematic properties of the newly prepared discogens containing a laterally substituted sidearm. A new strategy for the design of superior nematic discogens is explored by introducing laterally substituted sidearms (see figure). This modification is designed to enhance interdisc interactions only partially on the periphery of the disc to achieve a superior discotic nematic range and to lower transition points. Concurrently, steric hindrance between discs is introduced to prevent the formation of columnar phases.