Competing forces in the self-assembly of amide-functionalized discotic mesogens

Structure-property relationships of quinoxaline-based liquid crystals

Quinoxaline derivatives with different molecular structures stabilizing liquid crystalline self-assembly are discussed in this review. This class of molecules can be systematically modified with careful molecular engineering to achieve different molecular shapes, directing them to self-assemble into various types of mesophases. The structure-property relationships of such molecules and the resultant self-assembled functional structures are of utmost importance in organic electronic devices and related applications.

Adjacent functional group effects on the assembly of columnar liquid crystals

Although the impact of individual functional groups on the self-assembly of columnar liquid crystal phases has been widely studied, the effect of varying multiple substituents has received much less attention. Herein, we report a series of dibenzo[a,c]phenazines containing an alcohol or ether adjacent to an electron-withdrawing ester or acid. With one exception, these difunctional mesogens form columnar phases. The phase behavior appeared to be dominated by the electron-withdrawing substituent; transition temperatures were similar to derivatives with these groups in isolation. In most instances, the addition of an electron-donating group ortho to an ester or acid suppressed the melting temperature and elevated the clearing temperature, leading to broader liquid crystal thermal ranges. This effect was more pronounced for derivatives functionalized with longer chain hexyloxy groups. These results suggest a potential strategy for controlling the phase ranges of columnar liquid crystals and achieving room temperature mesophases.