SYNTHESIS AND CHARACTERIZATION OF LIQUID-CRYSTALLINE MAIN-CHAIN POLYESTERS FOR APPLICATION IN MIXTURES WITH THERMOPLASTICS

The melting points of liquid-crystalline main chain polyesters made from hydroquinone derivatives and substituted terephthalic acids can be lowered strongly by attaching flexible side chains or voluminous side groups. The solid state of poly(2'phenyl-1',4'-phenylene-2,5-dihexyloxyterephthalate is even amorphous with a glass transition at 47 degrees C and a phase transition to isotropic melt at 184 degrees C. Beside the low phase transition temperatures, this polyester is readily soluble in toluene and tetrahydrofuran. Up to 40 mol-% of 2,5-dihexyloxyterephthalic acid may be replaced by unsubstituted terephthalic acid without a strong influence on the phase transition temperatures and the solubility of the polyester. The E-modulus of the copolyester with 40 mol-% of terephthalic acid reaches 7700 MPa.