Liquid crystalline polymers VII. Thermotropic liquid crystalline poly(azomethine-ether)s containing dibenzylidene derivatives in the main chain

A new homologous series of thermotropic liquid crystalline poly(azomethine-ether)s based on dibenzylidene derivatives was synthesized by solution polycondensation of various diformyl-α,ω-diphenoxyalkanes, I–VIII with 2,7-bis-(m-aminobenzylidene)cycloheptanone IX and bis-(m-aminobenzylidene)acetone X. The inherent viscosities of the polymers were in the range 0.23–0.69 dl/g. All the poly(azomethine-ether)s were insoluble in common organic solvents but dissolved completely in concentrated H2SO4 and methanesulphonic acid. The mesomorphic properties were studied as a function of the diphenoxyalkane space length. Analysis by differential scanning calorimetry and optical polarized microscopy demonstrated that the poly(azomethine-ether)s from nematic mesophases over wide temperature ranges.