Side chain liquid crystalline diethanolamine-based polyesters with methoxy and/or nitroazobenzene mesogenic moieties

Side-chain polyesters based on diethanolamine and 5-hydroxyisophthalic acid with mesogenic methoxyazobenzene and nitroazobenzene groups were synthesized and their liquid crystalline properties were examined. Four different types of polyesters were prepared by using various combinations of monomers differing in the mesogen group and the length of the spacer. The thermal and structural properties depend on the type of polyester as well as on the side chain length. The glass transition and isotropization temperatures increase when the methoxyazobenzene group is bound to a diol and decrease when it is bound to an isophthalic acid. Most of the polyesters are thermotropic liquid crystals and form a nematic phase on heating. Some polyesters exhibit shear induced isotropisation to nematic transition up to 25 degrees C above the isotropization temperature.