Polyethyleneimine-based side-chain liquid crystal polymer exhibiting smectic B phase

A novel side-chain liquid crystal polymer (PEI-AzOH) was synthesized by the reaction of a branched polyethyleneimine (PEI) and an epoxide (Ep-AzOH) with 4-(4-(6-hydroxyhexloxy)phenylazo)phenoxy (AzOH) group. A side-chain liquid crystal polymer (PEI-AzBu) was also synthesized by the reaction of PEI and an epoxide (Ep-AzBu) with 4-(4-(butyl)phenylazo)phenoxy (AzBu) group. Their thermal properties and orientational behavior were examined. Ep-AzOH exhibited a nematic phase. PEI-AzOH exhibited smectic A and smectic B phases on heating and cooling processes. In the X-ray diffraction pattern of the smectic A phase of PEI-AzOH, the sharp inner and broad outer reflections were measured. On the other hand, the X-ray diffraction pattern of smectic B phase of PEI-AzOH consisted of the sharp inner reflection and one outer reflection. This suggests the formation of hexatic packing with long-range order within the layer. The bilayer structure was proposed for packing models of the smectic A and smectic B phases. PEI-AzBu exhibited the smectic A phase with a bilayer structure.