Side‐chain type liquid‐crystalline polyethers, 2 Effects of mesogenic moieties on the thermal properties and their self‐assembly behaviour

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Abstract
A series of polyethers having mesogenic moieties connected to the backbone without flexible spacer in the side‐chain were prepared by ring‐opening polymerization of the corresponding glycidyl ether derivatives containing various mesogens. As the mesogenic side‐chains, tolan and phenylene units with alkoxy or alkoxycarbonyl groups were introduced and compared with biphenyl type mesogens. The polyether with tolan derivative having butoxy group as the side‐chain end exhibited two kinds of highly ordered smectic phases. On the other hand, in the case of biphenyl or tolan as the rigid‐core, introduction of ester group as an end‐group decreased the thermal stability of liquid‐crystalline phase as compared with the case of alkoxy group as the end group. The polyethers with the p‐alkoxyphenyl group in the side‐chain exhibited a smectic A phase which formed a bilayer structure, while no mesophase was observed for those having the p‐alkoxycarbonylphenyl group in the side‐chain. The self‐assembly of bilayer structures, which consist of hydrophilic layer (polyether backbone) and hydrophobic layer (side‐chain), might be responsible for the appearance of liquid‐crystallinity in such polyethers whose mesogen consists only of a simple phenylene ring.