Multifunctional oxadiazole-based polycatenars : a pathway to polar columnar phases

Polar columnar liquid crystals (LCs) offer a promising pathway to nanostructured architectures for next-generation ferroelectric devices. Here, we present a robust design strategy for producing polar columnar LCs based on nonsymmetric π-conjugated 1,3,4-oxadiazole-derived bent-core polycatenars. The materials feature three alkoxy chains at one end and a single chain at the other, with the latter incorporating an azobenzene moiety that is either nonfluorinated or fluorinated to varying degrees. Increasing the degree of fluorination directs the molecular aggregation into novel modes of self-assembled columnar structures, leading to polar columnar phases. All phases could be perfectly aligned under an electric field due to the induced dielectric polarization from the oxadiazole ring. Notably, while nonfluorinated materials fail to form gels in organic solvents at low concentrations, their fluorinated counterparts exhibit exceptional gelation capabilities at concentrations below 1% weight, classifying them as supergelators. This behavior is due to enhanced π–π interactions and directed aggregation facilitated by aromatic core fluorination. Additionally, all materials exhibit reversible trans-cis photoisomerization upon light irradiation, both in the bulk state and in solution. These findings establish a versatile approach for designing multifunctional polar columnar phases through controlled molecular aggregation, which can be of interest for technological applications.