Structural behaviour of thermotropic liquid crystals from poly(4‐vinylpyridine) fully and partially quaternized with a mesogenic group

Liquid crystals were obtained from poly(4‐vinylpyridine) quaternized with 1‐bromooctane and 1‐bromododecane ω‐substituted with 4′‐methoxy‐4‐biphenyloxy mesogenic groups. Their thermotropic polymorphism was studied by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction. Three types of smectic mesophase, namely A, B, and E, were identified and described from a structural point of view. Their structure was found to be very similar to that previously reported for their monomer counterparts. The mesogenic pendant groups are arranged in single layers with the polymer backbones inserted in between. As a function of decreasing degree of quaternization, the smectic period increases slowly, reflecting the expansion of the sublayers containing the polymer backbones along with the free pyridine rings.