Hydrogen-bonded liquid crystalline materials: Supramolecular polymeric assembly and the induction of dynamic function

Liquid crystals are molecular materials that combine anisotropy with dynamic nature. Recently, the use of hydrogen bonding for the design of functional liquid crystalline materials has been shown to be a versatile approach toward the control of simple molecularly assembled structures and the induction of dynamic function. A variety of hydrogen-bonded liquid crystals has been prepared by molecular self-assembly processes via hydrogen bond formation. Rod-like and disk-like low-molecular weight complexes and polymers with side-chain, main-chain, network, and guest-host structures have been built by the complexation of complimentary and identical hydrogen-bonded molecules. These materials consist of closed-type hydrogen bondings. Another type of hydrogen-bonded liquid crystals consists of open-type hydrogen bonding. In this case, the introduction of hydrogen bonding moieties, such as hydroxyl groups, induces microphase segregation leading to liquid crystal-line molecular order. Moreover, liquid crystalline physical gels have been prepared by the molecular aggregation of hydrogen-bonded molecules in non-hydrogen-bonded liquid crystals. They show significant electrooptical properties. An anisotropic gel is a new type of anisotropic materials forming heterogeneous structures.