Effect of Atomic‐Scale Differences on the Self‐Assembly of Thiophene‐based Polycatenars in Liquid Crystalline and Organogel States

Two series of polycatenars are reported that contain a central thiophene moiety connected to two substituted oxadiazole or thiadiazole units. The number, position, and length of the peripheral chains connected to these molecules were varied. The oxadiazole‐based polycatenars exhibited columnar phases with rectangular and hexagonal or oblique symmetry, whereas the thiadiazole‐based polycatenars exhibited columnar phases with rectangular and/or hexagonal symmetry. All of the compounds exhibited bright emission in the solution and thin‐film states. Two oxadiazole‐based molecules and one thiadiazole‐based molecule exhibited supergelation ability in hydrocarbon solvents, which is mainly supported by attractive π–π interactions. These gels showed aggregation‐induced enhanced emission, which is of high technological importance for applications in solid‐state emissive displays. X‐ray diffraction studies of the xerogel fibers of oxadiazole‐based polycatenars revealed a columnar rectangular organization, whereas a hexagonal columnar arrangement was observed for thiadiazole‐based polycatenars. Rheological measurements carried out on the samples quantitatively confirmed the formation of gels and showed that these gels are mechanically robust. The impact of an atomic‐scale difference (oxygen to sulfur, <2 % of the molecular weight) on the self‐assembly and the macroscopic properties of those self‐assembled structures are clearly visualized.