Effect of linking groups on 2, 5-disubstituted thiophene with chalcone as the side arm containing bent-core materials

Novel bent-core materials containing a central core of 2, 5-disubstituted thiophene with chalcone as the side arm were synthesized and characterized to determine the structure–property relationship. The structural difference between two materials is the linking group in the thiophene and chalcone side arm. Chalcone is linked with thiophene by ester group in material I, while ester group is replaced with imine group in material II. The change in linking group exhibited a drastic difference in their physicochemical and intramolecular behaviors. Material I exhibits a hexagonal columnar mesophase at below room temperature, whereas material II exhibits a crystalline phase. Both liquid crystalline and crystalline properties were examined from polarized optical microscopy (POM), differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD) analyses. The highlight of this work is material I revealed a hexagonal columnar phase in the temperature ranges 22–38°C and undergoes photocrosslinking in UV light; contrarily, material II exhibits neither LC phase nor photocrosslinking property.