Tri-substituted s-triazines as mesogenic cores

Two series of equivalently-and inequivalently-tri-substituted s-triazines (as ESTs and ISTs, respectively) were synthesized and characterized in this study. More than one mesogenic biphenyl substituent were required to display mesomorphic properties, and two or three biphenyl substituents resulted in liquid crystalline textures under polarizing light. The mesophase transition temperatures for both IST and EST series are quite close despite their molecular weight difference. With longer sidechains, s-triazine for IST series formed a columnar hexagonal disordered mesophase (D-hd); while for the analogous compound in EST series, a perfectly aligned layered structure was found to be co-existed with the D-hd phase. With shorter sidechains, the s-triazines exhibited nematic mesomorphism.