Towards Room Temperature Biaxial Nematics

A series of new liquid crystalline compounds based on the 2,5-bis-(p-hydroxyphenyl)-1,3,4-oxadiazole (ODBP) core was synthesized in an effort to access the biaxial nematic phase at low temperatures. Derivatives with secondary terminal alkoxy groups and derivatives with either two or four lateral methyl groups were prepared. Secondary alkoxy terminal groups either suppressed mesophase formation altogether or increased the nematic onset temperature relative to primary groups. The dimethylated derivatives showed significant reductions in the nematic onset temperatures compared to the previously reported unmethylated compounds. The tetramethylated analogs generally possessed low clearing temperatures, but exhibited only monotropic mesomorphism