Preparation and properties of a series of thermotropic/lytropic main-chain liquid crystalline polymers

A series of main-chain polymers P₁-P₇ were synthesized by an interfacial condensation reaction of 4,4′-dihydroxy-α,α′-dimethylbenzalazine, a mesogenic monomers, and a mixture of terephaloyl and sebacoyl dichloride. The structure of polymers was characterized by means of IR. DSC, POM and WAXD were used to measure their thermal properties and thermotropic and lytropic liquid crystalline properties. Monomer DDBA and polymers P₁P₆ are nematic mesophase and exhibits clear thread-like textures. The thermotropic mesogenic property of polymers is weakened with increasing the concentration of the rigid chain segment. Polymers P₁-P₇ are lytropic liquid crystalline polymers and the textures of polymers in solution changes from multicolor willowy leaf-shaped texture to gravel-shaped texture for the increase of the rigidity of the polymer chain. The polymers P₁-P₇ are thermal stable up to about 320°C and the thermal stability is enhanced from P₁ to P₇.