Metallo-Responsive Liquid Crystalline Monomers and Polymers

A series of liquid crystalline ligand-containing monomers with chemo-responsive properties has been prepared and studied. These molecules are functionalized derivatives of the 2,6-bisbenzimidazolylpyridine (Bip) ligand. Tailoring the size of the aromatic core and the length of two pairs of alkyl substituents allows the preparation of mesogens with a range of tunable thermal liquid crystalline transitions and phases. The binding of lanthanide- and/or transition metal salts to the ligand containing mesogens results in a transition from a liquid crystalline to an isotropic state. Acyclic diene metathesis of the monomers yielded either oligomers or polymers, dictated by whether the alkene is either terminal or nonterminal, respectively. Both oligomers and polymers exhibit enantiotropic liquid crystalline behavior and become isotropic in the presence of metal ions.