Phase modulation of thermotropic liquid crystals of tetra-n-alkylammonium polyoxometalate ionic complexes

A series of composition analogous polyoxometalate-based ionic complexes are synthesized and studied, with a focus on the correlation between their mesomorphic behavior and their chemical structure. Generally, these polarizable rigid polyoxoanion clusters decorated with hydrophobic flexible alkyl chains have demonstrated a propensity to form thermotropic liquid-crystalline (LC) phases. Characterized by differential scanning calorimetry (DSC), polarized optical microscopy (PM), and X-ray diffraction (XRD), two of the four investigated complexes tend to form thermodynamically stable mesophases. Longer alkyl chains have been found to form mesophases, and the alkyl chain length of the quaternary ammonium cations influences both the occurrence and type of mesophase exhibited.