Synthesis and liquid crystal properties of thermotropic copolycarbonates composed of biphenyl and diphenylpropane moieties

Abstract Thermotropic liquid crystal copolycarbonates (below) were prepared by the melt polycondensation of mixtures of 4,4′-bis(6-hydroxyhexamethyleneoxy)biphenyl and 2,2-bis[4-(2-hydroxyethyleneoxy)phenyl]propane with alkylene diphenyl dicarbonates. The copolymers with n = 4 having high molecular weight were synthesized in high yields and showed better solubility in organic solvents, such as halogenated hydrocarbons and ether, than the copolymers with n = 2. All the copolymers form liquid crystal phases over the entire range of the composition. In the copolymers ( n = 2) eutectic temperatures have been observed but with the copolymers ( n = 4) the phase transition temperatures gradually increased with increasing content of the mesogenic unit. Comparison of the liquid crystal behaviour of the copolymers with that of the polymer blends indicates that the latter form better aligned liquid crystal phases. This means that the orientation of the mesogenic unit is disturbed by the polymer chain in the copolymers but, in the polymer blends, the orientation is retained without interruption.