Polar columnar liquid crystals (LCs) with a polarization along the columnar axis are promising for the development of ultrahigh-density memory devices. They can have so-called ferroelectric switching properties, where polarity of a material is reversed by an electric field. It is difficult to realize polar orders in fluidic media.
Byoung-Ki Cho, Dankook University, Chungnam, Republic of Korea, and colleagues have designed a ferroelectrically switchable columnar LC. The team assembled a double-stranded helical column (pictured), similar to DNA, from cisoid 1,2,3-triazole-functionalized naphthalene molecules. The molecule was prepared by Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC), which is a representative click reaction.
The triazole unit has a high dipole moment and can form hydrogen bonds. Application of an electric field to the columnar LC at 105 to 115 °C causes the triazole to rotate and switch orientation along the helical axis of the column, relative to the direction of the electric field. This changes the overall polarization. The hydrogen bonding along the columnar axis is weakened at these higher temperatures; the phenomenon is not observed at 80 °C.
According to the researchers, they have discovered the first ferroelectric columnar material using 1,2,3-triazolyl groups as the polar functional unit. This finding may be significant for next-generation ferroelectric memory devices.
- Ferroelectrically Switching Helical Columnar Assembly Comprising Cisoid Conformers of a 1,2,3-Triazole-based Liquid Crystal,
Manh Linh Nguyen, Jaeduk Byun, Suwoong Kim, June Won Hyun, Kahyun Hur, Tae Joo Shin, Byoung-Ki Cho,
Angew. Chem. Int. Ed. 2018.