LIQUID-CRYSTALLINE MAIN-CHAIN IONENE POLYMERS

In this survey, the thermotropic and/or lyotropic liquid crystalline (LC)properties of main-chain ionic polymers, including viologen polymers, are discussed. Combination of their respective LC and ionic properties into a single polymer structure is of obvious interest and relevance from a number of different perspectives. Because of the presence of strong ionic interactions, especially in the case of a small-sized counter-ion, they tend to decompose in the melt and, therefore, preclude the formation of a thermotropic LC phase. However, suitable chemical modification, including the incorporation of large hydrophobic counter-ions, enables the preparation and characterization of thermotropic main-chain ionic polymers. Furthermore, their lyotropic properties in common organic solvents, especially those of viologen polymers, may open a number of avenues for the practical exploitation of these materials in the fields of films, coatings, polymer blends and composites. Current understanding of LC main-chain ionic polymers is incomplete, but improvement will no doubt provide an enlarged scope for the applicability of this novel class of LC polymers to new and diverse frontiers in materials science and technology.